If the likes of Cod and Halo put you off with their blatant disregard for reality, then Operation Flashpoint 2: Dragon Rising might be just your type of game, as but one bullet can end the game. And for just £7, it's a steal at Play!
This is the cheapest deal around at the moment, and for quite a recent game that was rather well-received in the hardcore community, it's a very good price. Delivery, as per usual, is free, and it's in stock, so hurry before supplies deplete!
The Operation Flashpoint series champion a realistic approach to FPS gaming. A single bullet can kill you, and your health won't simply recover over time. They've spent a lot of time and finessing the AI, ensuring they act and attack like real soldiers. Dragon Rising, which, sadly, has no real dragons in it, is the first OF game to take the next-gen step, and as such has been bolstered with a vast viewing-distance, realistic bullet-penetration, and a huge island to explore at your leisure.
Dragon Rising isn't for everybody. You'll have to plan your approach, stage your attacks with squad-commands and fire at the enemy as a real soldier would. No charging in, gung ho. Burst fire, from cover, and only progressing forward with the enemy flanked or under fire. If you can learn to shed your old FPS ways, then Dragon Rising is a hugely rewarding game. It's got a vast, lush island to explore, and a palpable sense of atmosphere that shouldn't be missed.