Electric. Not only is it a powerful force, it's also got a variety of uses. Hell, a Pikachu would be the only companion you'd ever need. Plus, NO MORE F****** $450 ELECTRICITY BILLS!!
And, it's just plain cool.
-Fire is powerful, but it's been killed dead, at least in my opinion.
-Water is kinda boring. Sure, it's powerful, but it just can't compare with the raw power of lightning.
-Ice is decent, but it just doesn't have the sheer killer edge of electricity.
-Fighting is pure physical power. Strong, yes, but punching an electrified object is never a good idea.
-Grass, interesting. Seeds, poison, etc. Nature is all-conquering, but it just isn't as cool. Which would you rather watch, grass growing or an electrocution?
-Rock, Ground, Steel are all basically "smashie-smashie!" Fun, but also kinda plain.
-Ghost is interesting. I'm a paranormal freak, but since Pokemon ghosts aren't actually associated with undeath, it's not as cool.
-Bug? I don't even like REAL bugs :/
-Poison is a great way to kill someone, but unless it's one of those torture-poisons, it's just not as much fun to watch.
-Dragon seems a bit odd to me. It's resistant to a lot of different types, has limited weaknesses, and it's moves are some of the higher level ones availiable. It's probably my runner-up.
-Chuuuu...
DON'T FLAME ME! THESE ARE JUST MY OPINIONS!!