For the Battle Subway and PWT: Truant Durant.
1) Use Entrainment.
2) Switch out to a Baton Passer like Smeargle.
3) Set up Shift Gear or Quiver Dance or any set up move you have while using Protect on the attacking turns of Truant.
4) Use Substitute when the opponent can't move then Protect next turn
5) Baton Pass to the Sweeper of your choice.
The only Lead Pokemon for the Leaders and Champions that has anything to counter Entrainment Durant is Brock's Onix with Protect in the Kanto Leaders Tournament but even with that, unless he uses it every other turn, you got nothing to worry about (It's only attacking move is Sand Tomb). Plus the AI is stupid enough to not switch out when it gets Truant.
I've never used it before but I really do want to try it out.
This actually sounds like a lot of fun.
Now to get my hands on one of those Durants....
Venemo Oscuridad - 8 Battles
Anyone who says all pokemon are created equal cearly hasn't had much experience with Unown.