There are a lot of good Pokemon you can get, but these are my personal favorites:
- Kricketot (when it evolves, at least). With Technician + Fury Cutter, it really destroys everything early game, but it sucks after about the third Gym. (Before 1st Gym)
- Mystery Egg. If you find all the Police Officers, breed a Growlithe, and trade the Egg to the Police Officer, you can get an Egg that you can get 1 of 18 great Pokemon from, such as Larvesta and Frillish. (Before 3rd Gym)
- Bunnelby. Huge Power is nothing to laugh at, although it's kinda rare. (Before 3rd Gym)
- Lillipup. Gets quite a few coverage moves and has a nice Attack. (Before 2nd Gym)