Gigantic online shop Amazon will pay for your old games.
Box-up Medal of Honor, print out a special pre-paid delivery label and send your item off and in return you'll get an £23 Amazon Gift Card credited to your account. Do the same for Just Dance 2 and get £15. Repeat for Assassin's Creed: Brotherhood and get £28.
Once your old game has been received, Amazon will email you to say yes, you can have the money or no, your game was broken we're sending it back. The latter can take up to two weeks. And in some cases, faulty goods may be thrown away.
If you get a yes, the money will be credited immediately.
Note that Amazon will only accept up to three game trade-ins from you in three months - a limit that seems very low.