Skyrim, for the Dragonborn and Dawnguard DLC. An extra 20 bucks. Would have been 40, but I bitched to microsoft that DB kept freezing my machine and they gave me a refund, so I bought the DG one as well once that money came back to my account.
Or perhaps Borderlands 2, I bought all the little extra area DLC missions except for that Tiny Tina DnD parody campaign or whatever it was. I like this game but some of this shit is simply impossible for me because I can never find good weapons even when farming loot midgets for half a day. Honestly liked BL1 a lot more because even solo it never felt like you were way out of your league and the drop rates for good stuff didn't make me want to throw the disc out the window.