My local blockbuster has a promo on just now, where they are getting rid of TONS of stock to shift quick on dvd/ps2/xbox and xbox 360.
The games are preowned but all play fine and you get the usual blockbuster 3 month guarantee.
They dont come with covers and only some have instructions, but there ULTRA cheap!
It's a buy 2 get 3rd free promo on them too (cheapest 1 free).
It's selected stores ONLY, this is not nationwide, so ask around.
I picked up halo 3, mass effect, and bioshock for £8.
Then i got call of duty 2, call of duty 3 and oblivion for £11.
(Most of the games were £4 & £7 on their own).
£19 in total for 6 Xbox 360 games is not bad at all, considering they were selling halo 3 for £29.99 on its own still!