OK...
Crazziikiid, other people shouldn't be picking your team members for you. You should be choosing them yourself, because no-one here knows what your preferences are. I could tell you to use Garchomp because he is immensely powerful and can rip through entire teams with ease, but if you don't like Garchomp then I've just wasted my time suggesting it to you (although Garchomp is Gen IV only, you should get where I'm coming from.) Put simply, you need to choose your final three team members yourself.
This is what you should be aiming for. Since I'm assuming this is in-game, I'm omitting Natures and Hold Items:
Swampert @ Anything
- Earthquake
- Rock Slide
- Brick Break
- Surf/Muddy Water
Swampert's Attack stat is better than its Sp.Attack, although its Sp.Attack stat is certainly not bad. Earthquake is Swampert's strongest STAB Attack, Rock Slide takes out Flying-types that can avoid Earthquake, Brick Break for extra coverage and barrier-breaking usefulness and finally either Surf or Muddy Water in the last slot for double STAB (which never hurts.)
Skarmory @ Anything
- Aerial Ace
- Steel Wing
- Spikes
- Roar
Skarmory is more defensive than offensive, so might as well make the most of that Defense stat. Aerial Ace and Steel Wing both give you STAB attacks, Spikes combined with Roar allows for a more indirect way of dealing damage whilst possibly allowing you to tip the tide of the battle in your favour by forcing out a less troublesome opponent on an enemy trainer's team.
Linoone @ Sitrus Berry preferably
- Return
- Belly Drum
- Shadow Ball
- Thunder Wave/Rock Smash/Dig/Anything really
Simple really: Use Belly Drum to max out your Attack stat, then start murdering everyone with STAB'ed Return - the Sitrus Berry will cushion the 50% HP loss suffered from using Belly Drum. Shadow Ball is for Ghosts that resist Return, and the last slot can be anything you like really
Heracross @ Whatever you like
- Brick Break/Reversal
- Megahorn
- Earthquake/Rock Tomb
- Swords Dance/Bulk Up/Aerial Ace
Heracross is a demon when it comes to attacking, so load him with a ton of Physical Attacks to turn him into a beast. Brick Break and Megahorn provide extremely hard-hitting STAB attacks for Heracross, third attack provides extra coverage (no Rock Slide TM sucks a bit,) and the final move can either be a stat-booster like Swords Dance or Bulk Up, or another attack such as Aerial Ace for those vile Double Team spammers.
I'll help you with your final two team members once you figure them out, although I'm going to let you decide just what those two Pokemon will be.