Personally, I think the fun of the game is catching Pokemon without planning it out. It's really not as much fun when you get six Pokemon you've wanted from the start and level them up, so much as it's fun to catch Pokemon and raise them into strong battlers.
Therefore, I don't have a team set-in-stone, but I think I'll have Cyndaquil and/or Totodile (I'll most likely start with Cyndaquil and try to get a Totodile), the Red Gyarados at some point (or Shellos, if that beta sprite is ever used; if I can't get a Totodile, the Red Gyarados or Shellos will be my water staple), maybe Togekiss, as a Flyer (and possibly healer, if I can somehow get my Togepi with Softboiled onto HeartGold).
So, in short:
Cyndaquil
Totodile/Red Gyarados/Shellos
Togepi
...the rest is up to chance encounters. I may eventually want a Gliscor, Mamoswine, Tyrannitar, Bulbasaur, etc., but it all depends on availability.