Best Game Deal you ever got.

Hmm....though the games itself are not some of my all-time favorites, just flat out deals for me I would say would be this bundle of four video games (all PS2) from eBay for nothing more than $14. The games were X-Men Legends 1 and 2, Mortal Kombat: Deception, and Legacy of Kain: Defiance. I have yet to play two of those games (both for story reasons...I don't like playing anything ahead of previous installments, except for fighting games and a few other exceptions here and there). That isn't to say I don't enjoy the games (at least the two that I have actually played xD), I do, but they aren't a couple of my favorite games ever. I am not far into X-Men Legends 1, so maybe I'll enjoy it more as it progresses and as the story unfolds (which I am sure I will). As for Deception, I haven't played it in quite some time, but...yeah, it's fine and fun.

i got gears of war for free with my xbox

This isn't a deal in the conventional sense, but when I was 11 years old, my friend gave me Army Men:Sarges Heroes for the N64. At the time, I didn't know that every Army Men game (with the exception of the Air Attack games) was total garbage. All I did know was that the game was Rated T for Teen,  which my parents deemed was a bit out of my age zone(though it didn't stop me from playing Perfect Dark or Conker's Bad Fur Day.) Anyway, my parents decided to return the game and let me choose something else out, so I picked, almost randomly, Rayman 2: The Great Escape(which, if you don't know, is one of the few truly great 3-D platformers, and may very well be the apex of the genre.)
So thanks, ratings board. Thanks to you, I got Rayman 2 for free.

rarepcgames.com has given me some great deals. Also I got that game Flatout: Ultimate Carnage for like 2.50 at best buy.

Mass Effect -$10
Battlfield 1943 - $15

Bioshock for $4.99 on Steam.

Not sure if it's the best but I picked up MGS2 for about £2 pre owned in gamestation in good condition.

Probably TF2 for about £10 on Steam.