There are more than 15 to choose from, but here are the easiest moves to pull off. I suggest doing an AR challenge (as Batman) where the enemies spawn infinitely.
(Move - controller prompt)
Strike - X X X
Counter - Y
Evade - A A
Stun - B
Super Stun - B B B
Aerial juggle - B B B X
Beatdown - B X
Ground takedown - RT+Y
Batarang - LT
Batclaw slam - LT+Y X
Quick explosive gel - LT+X
Quick REC- LT+B
Freeze grenade - RT RT
Special Combo Batarang - hold LT
Special Combo explosive gel - hold LT+X