Hmm, Breloom is pretty great, so is Venusaur, Zapdos, Galvantula, Snorlax, Charizard, Blazikan, Swampert, Sceptile, Lucario, Dragonite, Garchomp, Garbador, Voltorb and of course Magikarp.
If I had to narrow it down I'd say...Zapdos I guess, or Lucario. Both of them are bloody awesome.