Gale Wing Srock, take Shrewd the Sandshrew.
Shrewd hates to waste moves with normal effectiveness attacks, so here's the kicker - you may only attack a Pokémon if you can hit it for Super Effective damage. If it can't deal SE damage, it must immediately switch out to something. You may not use any moves that raise stats by less than 2 stages, because Shrewd believes that it's a waste of time to raise stats one stage at a time. Also, it may not use any moves with an accuracy below 90, because it thinks that's too much of a waste to miss. You may evolve freely, but once it evolves, you may not change any of its moves.
tl;dr:
Shrewd hates to waste moves with normal effectiveness attacks, so here's the kicker - you may only attack a Pokémon if you can hit it for Super Effective damage. If it can't deal SE damage, it must immediately switch out to something. You may not use any moves that raise stats by less than 2 stages, because Shrewd believes that it's a waste of time to raise stats one stage at a time. Also, it may not use any moves with an accuracy below 90, because it thinks that's too much of a waste to miss. You may evolve freely, but once it evolves, you may not change any of its moves.
tl;dr:
- Only use SE attacks; if it can't, it must switch out
- No stat boosting by less than 2 stages at a time.
- No moves with an accuracy below 90.
- Moveset is locked on evolution.