Hm. Difficult question there - there are many Electric types I like and much like any other type I find it impossible to choose one favorite. However, here are a few that are rather leading candidates for Exhibit A. In no particular order...
Electabuzz
Electabuzz is one of the species I've always really liked - My mind interpreted their sort of... strange headed feline-primate synthesis design as something awesome (so awesome that it eventually somewhat diverged even more from the source and became its own thing - one of my most personally significant species) and the sheer diversity of what they can do only made me appreciate them more. They're the only part of their evolutionary line I really like (I'm not a big fan of Elekid and I loathe Electivire with a passion), but as they're viable enough even without evolving, I can just continue to blissfully ignore the Tentacle-Rape-Robotnik-Evo. XD
Joltik and Galvantula
Three words. Electric Goddamn Spiders. What's NOT to love?
It also helps that both have utterly adorable designs (Of course, I find spiders adorable in general - but Joltiks and Galva are adorable even by non-spider standards!), a unique (for now) type combination with one of my favorite types and a very nice Special Attack stat (with the right sort of moves to take full advantage of it - especially when Thunder with Compoundeyes-augmented accuracy is involved).
But does one really need a reason beyond electric goddamn spiders? I don't think so.
Ampharos
I always found Ampharos' design to be rather interesting (especially following the adorable but basic Mareep and the bizarre pink-poodle-sheep Flaaffy) - smooth with an almost vaguely dinosaurian shape, It's been alluded to be some kind of awesome dragon-sheep since its inception (with a Japanese name that means either 'electric current' or 'electric dragon'). I was rather pleased to see it get Outrage as a tutor-able move in Gen 4 and even MORE pleased to see the thing finally dropping all pretenses and Super-Special-Awesome-Evolving into a Dragon-type with the most fabulous hair known to man or sheep. (Of course, right in time to walk into a herd of gogdamn fairies. Typical!)
Rotom
There's no way around it: Rotom is fricking adorable. The idea of a mischievous electric ghost possessing appliances was pretty clever (and is a nifty spin on the concept of aviation gremlins), the alternate formes are rather fun (some moreso than others - I have a bit of a personal bias towards Cut Rotom because... yeah, Grass-type. Plus, the thing amuses me greatly) and it has ALL the RP awesomeness potential (I need to write more of Siegfried somehow <<). Yeah. Rotoms are great. That is all.
Magnezone
I've never been a huge fan of Magnemite and Magneton always seemed like an incredibly lazy cop-out to me. Suddenly, enter Magnezone with its actually an evolution design and great usability and single-handedly saved the entire line for me, turning it from a forgettable side-electric into something I actually enjoyed using a fair bit.
Eelektross
I admit, I haven't trained one of these lovely things yet. The fact they take freaking forever to find and evolve (by which point I usually already have a great Electric-type) prevented me from trying the thing out myself. However, I love their design (fucked up alien lamprey things ftw), their type/ability combination which makes them a significant threat to most things that aren't Mold Breaker Haxorus with Earthquake and the sort of havoc they can wreak upon the unsuspecting. Now if only they weren't so obnoxious to get!
Honorable mentions go to Lanturn (for being adorable and a Deep Sea Anglerfish at the same time - only detracted by the fact there's nothing they can do that Lapras can't do better), Manectric (Great design, slightly less great usability), Raichu (for being the only one of its overpopulated-bullshit-cartoon-rodent type that is actually somewhat nifty looking), Raikou and Zekrom (both great designs but not on the list because they're Legendaries).
Also Stunfisk. It's fucking hilarious. Almost as gloriously derp as ALMIGHTY 'SPARCE but not quite.