Level select and all vehicles:
At the character select screen, press Y, Z, X, L.

Get Kevin Nash:
At any game menu, press L, X, Z, Y.

Get Ric Flair:
Beat Season Mode with The Big Show, Rob Van Dam or Triple H.

Get Lita:
Beat Season Mode with Matt Hardy.

Get Christian:
Beat Season Mode with Chris Jericho or Edge.

Get Bradshaw:
Beat Season Mode with Brock Lesnar.

Get Vince McMahon:
Beat Season Mode, facing Vince in the final battle.

Get Stephanie McMahon:
Beat Season Mode with Kurt Angle.

Get Hulk Hogan:
Beat Season Mode with The Rock, Edge or Kevin Nash.

Demolition Derby mode:
Win a match without firing any weapons.

Thanks to Revolution readers Matt Copeland and Barnaby!