Lara Croft and the Temple of Osiris

You can get this playing solo with two controllers if you don't mind doing some joypad juggling. Sign in with another account (or as a guest) with a second controller and play through one of the main tombs (I did the Tomb of the Timekeeper). Some parts require briefly using both controllers at the same time or quickly alternating between the two.

To get the most gems just make sure you use your main account to collect any gems. It's easy to track each character's score as you progress through the level.