Although, it is the #1 Pokemon used in UU, the most threatening that is. It can utilize Swords Dance also, catching people of guard thinking it would be specialized. To be honest, I haven't seen a Shaymin at all... Only on Shoddy though.
Shaymin has base 100 Speed, which is incredibly common. I have it Scarfed for two reasons:
a. Anything Timid/Jolly outspeeds me
b. Shaymin's Speed IV is 29, so anything with base 100 Speed and 30-31 Speed IVs goes first.