I chose on the basis of unlocks that stick to the core of the class while still creating new and interesting facets of play.
Scout:
-Soda Popper, Bonk, Sandman
Soldier:
-Direct Hit, Gunboats, Market Gardener
Pyro:
-Backburner, Detonator Axtinguisher
Demoman:
-Loose Cannon, Sticky Jumper, Ullapool Caber
Heavy:
-Brass Beast, Dalokohs Bar, Fists of Steel
Engineer:
-Frontier Justice, Wrangler, Gunslinger
Medic:
-Crusader's Crossbow, Kritzkrieg, Amputator
Sniper:
-Sydney Sleeper, Jarate, Bushwacka
Spy:
-Diamondback, Your Eternal Reward, Dead Ringer (Red Tape Recorder too if we're allowed)