Pachirisu is the "Pikachu" of the 4 Generation of Pokemon, meaning it's cute and cuddly, but doesn't do much outside of that. Decent HP for a Basic (70), the usual Electric Weakness to Fighting and Resistance to Steel, and one Retreat Cost. It can either search your deck for a basic Energy via Minor Errand Running or deal light damage with Thunder Jolt, which also may do 10 damage recoil to you.
Modified - 1/10 (No real reason to play this)
Limited - 8/10 (Great HP for a Basic, so it can live a while here)
Unlimited - 1/10 (Definately no real reason to play him here)