Cheap fairly modern games. Suggestions?

Ok so I take my gaming seriously. Not the kind of guy that will miss going out with his friends to play games. But I take it seriously. I am up to date with my games, such as Halo 4, Fifa 13 , Hitman, ( NOT COD, JUST NO ), etc :P
Recently I found my self bored from over playing my usual games, so I want to buy some new games, while keeping in mind I dont have a lot of money to spend. I have noticed a lot of great games from 2011-2012 that go for 10-20 pounds/euros, and you think to yourself '' THIS IS A MUST HAVE ''

Example: Dishonored, Resident Evil 6, Medal of Honor: Warfighter, Sniper Elite, Dragon Age 2, and the list goes on.

But I'm wondering, what's your cheap MUST HAVE game?  

Thank you :) 

doom 3

far cry 3

The Witcher 2, $30 new at any retailer. 

Red Dead Redemption

Dark Souls

Mass Effect 1 and 2

These aren't very old and should play them

Portal 2, Rayman Origins, Gears of War 3, Batman Arkham City, Binary Domain, Sleeping Dogs, Spec Ops, Darksiders 2, Mass Effect 3 and so many more.

Borderlands & Borderlands 2
Mafia II
Saints Row The Third
Halo Combat Evolved Anniversary 

Good question.  I'd suggest trying out Dragon's Dogma, though if you wait a month or two you'll be able to get the new edition with the DLC and it's going to be sold for $40 (good deal since Capcom won't sell the DLC seperately and the enjoy screwing over the ones who bought the game originally came out) and I found it to be the best fantasy set RPG of last year.

Deus Ex: Human Revolution/Dark Souls/Mass Effect (though, maybe wait to get the trilogy set it may end up being cheaper and at the very least will go down in price probably soon enough).

RDR

Battlefield 3 is down the $20 (12 pounds, 14 euros) used at Gamestop

Dead Space and Bioshock are must have, really cheap now too!