Hey reddit, I have a gamestop gift card good enough for 1 game. What should I get?

GAMES I ALREADY HAVE:

1. All assassin's creed games

2 Cod, BF3

3. Skyrim, Saints Row the third Fallout New Vegas (not Fallout 3), oblivion and the mass effect series

4. Portal 2 (hell yeah)

5. Gears, Halo, Fable and SC2.

I haven't tried any of the batman games yet, but I will probably get arkham city, unless im convinced to play arkham asylum, btw, are the force unleashed games worth it? Or should I get KOTOR or Battlefront 2 (I used to have those)

I honestly don't know what I should get