This was extremely hard to answer as there are so many Pokemon I like, and my favourites seem to change quite a bit as well. So I decided to add an 'Honourable Mentions' list as well.
Anyway, on to my top 10s:
1# Virizion - People who know me on here probably saw this coming from a mile away, but yes, Virizion is my favourite Pokemon of all-time. I can't exactly say why I started liking Virizion in the first place, but I guess I just felt this connection with it or something. It was mostly it's design that drew me in, and even now I still think it is a very well designed Pokemon. The colours fit together well, nothing in its design feels out of place, and overall it just looks very pretty to look at. I even think the shiny is nice, despite my dislike for pink.
I also like its Grass/Fighting typing, which is a typing it shares with Breloom and Chesnaught, two other favourites of mine.
Virizion may not be the most powerful Legendary Pokemon out there, but I really liked using it in White and Black2, and even in Y and ORAS. I thought it had a decent move selection, and stats.
Another thing I like about Virizion is how in legends it protected Pokemon, and I thought that was pretty cool and it just makes it even more badass in my eyes.
There are many more reasons as to why I love this Pokemon so much, but I think that'll do for now. I've still got 9 more Pokemon to go!
2# Blaziken - Another insanely badass Pokemon. Blaziken has been a firm favourite of mine ever since I played Pokemon Sapphire, my first Pokemon game. Since it was my first starter Pokemon, obviously there are some nostalgic reasons as to why Iove Blaziken so much.
I'm also a massive fan of Blaziken's design. It's awesome, sleek, and not over-the-top with details. I especially love the way GF designed its legs and face, and also its head-feathers. Mega Blaziken is nice looking as well and I really dig the fire ribbons on its arms, and the black fire-like details.
Another thing I really love about Blaziken is how strong it is, especially with its OP Hidden Ability Speed Boost. Seriously, Blaziken is without a doubt one of the strongest, most useful starter Pokemon I've used. The only other starters I've used that come close to it is Empoleon, and possibly Samurott. Not to mention its Mega Evolution is also super powerful.
So yeah, Blaziken is awesome, nuff said.
3# Snivy - My favourite unevolved starter by a longshot. Snivy is cute, whilst also being super cool at the same time. Not to mention it is smug AF.
First of all, I love its design. It has a nice colour palette, an appealing design that doesn't try to be 'sickeningly cute' like some other starters, and it always has that snobbish look on its face. It just knows it's as cool as heck. Shiny Snivy is also very nice looking.
Secondly, Snivy was the Pokemon that drew me back into the franchise. After playing all the Gen III main-series games I kind of moved on from Pokemon a bit. Well, that was until I saw Snivy. As soon as I saw it I instantly loved it, so much in fact that I got Pokemon White just so I could pick it as my starter. Obviously I remembered how awesome the Pokemon games were and, well, the rest is history.
Snivy may not be the strongest starter out there, and I may be pretty neutral towards its evolutions (I don't love them nor hate them), but I will always love the smug 'lil dude.
4# Samurott - Oh look, another Unova Pokemon. It's probably kind of obvious now that I love Gen V Pokemon, unlike a lot of people.
Anyway, Samurott is a freaking beast and I love it.
Once again, I mostly like Samurott due to design reasons, but I also like it because it is very decent to battle with. I don't think it is amazing competitively from what I've heard, but oh well, I'm more of a casual battler anyway.
So back on to its design and whatnot. I think Samurott has an awesome design, and I prefer it a huge load over Oshawott and Dewott. I love the colour palette GF chose for it, its badass shell armor, and its manly beard whiskers. I also appreciate how it is a quadrupled, but can also become bipedal when fighting with its, um, shell swords?
Oh, also really, really like shiny Samurott. It doesn't change drastically from the original but still manages to be nice looking.
5# Spritzee - My favourite little Puffy Plague Doctor Birb.
Spritzee is like Snivy in a way, as in I loved both of them as soon as I first layed eyes on them. I remember letting out a little 'squee' when Spritzee was first revealed in CoroCoro, and ever since then it has been creeping its way up and up my favourites list. Eventually it even managed to overtake Pyroar and become my favourite Kalos Pokemon.
My love for Spritzee comes completely from it's design, as I have never actually used one in-game before. The thing Iove about Spritzee the most is its puffiness and its adorable little, well, everything really. Though its face and little feet are especially cute.
The fact that Spritzee is based on Plague Doctors makes me like it even more, because y'know, they're badass and all. I love how GF managed to make something so cute, round, and fluffy, and base it off something thats well known for being creepy (and awesome).
I just hope that one day Spritzee gets the creepy Plague Doctor-themed evolution it deserves. Not that I hate Aromatisse or anything.
6# Incineroar - I'll admit when the final evolutions for the Alola starters were leaked back in May, I wasn't overly impressed with Incineroar. But over time the heel wrestling tiger grew on me a lot (along with Primarina), to the point I wanted the leaked starters to be the real deal. To my luck, and complete joy, they were. I ended up choosing both Litten and Popplio in Sun, but guess who ended up growing on me the most? You guessed it, Incineroar. Don't get me wrong, I absolutley love Popplio and Primarina (who's even in my honourable mentions list), but Incineroar just has so much personality and character that I can't help but adore it. Heck, it even made me fall in love with Litten, who I wasn't a fan of at first when it was revealed. Now it's my second favourite Fire-Starter. I'm neutral on Torracat though, but then again I usually feel that way towards the middle-stage starters.
Anyway, back onto the subject of Incineroar.
So a lot of people will probably disagree with what I'm about to say here, but I freaking love Incineroars design. It's glorious. One thing I absolutely love is how they added fur on its shoulders to make it look as if it is wearing a shirt with the sleeves torn off. I also love the look on its face,
Now onto Incineroar battle-wise. While I'll admit my Incineroar, Blitz, wasn't quite as strong as my Primarina or Salazzle, she still helped a ton during my playthrough and got me through some challenging battles. I also thought she had a decent move selection, and I loved the move Darkest Lariat.
One last thing. I really like Incineroars Fire/Dark typing, and I'm glad GF didn't go with Fire/Fighting again.
7# Raikou - Tigers are cool, and Thunder and Lightning is cool, so mix them both together and you get this beast of a Pokemon.
To be honest, when I first got into Pokemon Raikou was my least favourite out of the Johto Beasts. I was always more of a Suicune fan. After seeing it in Zoroark: Master of Illusions, I realised how badass Raikou really was, and after that it didn't take too long for Raikou to become not only my favourite Johto Pokemon, but also one of my favourites overall.
I love Raikous design, especially its saber teeth and storm cloud-like mane. I also love its shiny form.
I've never used Raikou in-game before, but hopefully I'll be able to soon in Pokemon Sun.
8# Lopunny - A really awesome Pokemon with an even cooler Mega Evolution. I've always been quite fond of Lopunny, but it wasn't until recently, when it got a mega, that I really started liking it. Like, a lot.
I love the designs for both regular Lopunny and Mega Lopunny, especially the latter. I particularly love how Mega Lopunny looks like some type of female fighter. As for regular Lopunny, I just love the fluffiness of it.
Another thing I like about Mega Lopunny in particular is its typing of Normal/Fighting. It's such a cool type combo in my opinion, and I'm glad GF chose it. I think I like it so much because I like both Normal and Fighting types.
I haven't used Lopunny to much in-game, but from what I've experienced it seems to be a decent Pokemon, especially its mega evolution. If we do get DP remakes I'll definitely be having a Lopunny on my team, thats for sure.
9# Salazzle - Such a badass Pokemon, with a wickedly cool design as well. Salandit always had a firm spot on my planned team, but after seeing Salazzle in the datamine, Salandits spot was now cemented.
Ok, so firstly onto the design. I love it, love it, love it! I love how sleek she looks, the pink and purple markings on her hands, feet, and body, and the ribbons that come off of her back. She kinda reminds me of an assassin actually, hence why I named my Salazzle 'O-Ren Ishii' after the character from Kill Bill. Also I'm usually not a fan of white-coloured shinies, but Salazzle is definitely an exception, as it actually looks quite pretty.
Salazzle, in my opinion, is beast to battle with. Sure, she may not have the best defense out there, but she can deal some pretty serious damage as I found out. I always had my Salazzle at the front of my team for this reason, and the fact that I just felt so cool using her. I thought Salazzle had a nice range of moves, and her Fire/Poison typing is not only unique, but flat-out awesome. I always wanted a Pokemon with that typing, and I'm so glad that she and Salandit were the ones to get it.
So yeah, Salazzle is awesome AF.
10# Breloom - Mushroom, Kangaroo, Dinosaur hybrid that can beat the crap out of you. Whats not to love.
I love Brelooms design. It's just so interesting to look at, and its not just a generic looking dinosaur like some other Pokemon are. I love its little mushroom hat, and expandable arms in particular. I also love the colour palette in both its shiny and non-shiny forms.
Breloom is also great to battle with in-game, from my experience anyway. I've also heard that it goes quite well in competitive as well. Max Jr, my Breloom in Alpha Sapphire was a beast, and I used her almost as much as I used my Blaziken. I found her to be very useful, and her movepool was pretty damn good.
Another thing I love about Breloom is it's Grass/Fighting typing, as I stated before in my Virizion comments. It's gotta be one of the coolest typings, since I love every single one of the Pokemon that has it.
I really hope that someday Breloom gets a Mega Evolution as well, if they even make more, that is...
11# Jolteon - I know the title says only 10 Pokemon, but I couldn't help but add one more. Originally this place belonged to Golisopod, but since then I've realised there is another Pokemon that I like slightly more than it, and that is Jolteon, who was originally on my honourable mentions list.
Eeveelutions are usually a bit of a hit or miss with me. If I like one, I really like it. If I don't like one however, then I really don't like it *cough, cough*Umbreon*cough, cough*.
Jolteon is one of the ones that I really, really, really like (along with Glaceon, Espeon, Vaporeon, and of course, Eevee). Obviously, if I hated it it wouldn't be in my top 11.
Design-wise, I think Jolteon has one of the best of the Eeveelutions. It's simple, but effective at the same time. I love how it is less 'cutesy' than it's other Eevee-evolved brethren, but at the same time still manages to have that 'charm' that people find in the rest of the eeveelutions.
In game, Jolteon is speedy as feck. It also has pretty good range of moves, and it's attack stat is decent as well. Definitely one of the better eeveelutions out there.
Also, Jolteon is an Electric-Type, and Electric-Types are cool.
HONOURABLE MENTIONS(In Order): Pyroar, Black Kyurem, Magby, Aggron, Wailord, Empoleon, Giratina, Golisopod, Chesnaught, Primarina, Lycanroc (Midnight), Shaymin, Ho-oh, Venusaur, and Dragonair.