Rainbow Six Vegas
I, for one, welcome our realistic shooter masters. I've been waiting for Rainbow Six Vegas ever since its announcement, and it is better than I could've hoped. Playing through Vegas is a dream come true. Go buy this game right now. If you're still here, let's discuss some of the finer points in the game.
There's something wonderful about taking cover behind a slot machine. Each engagement area is full of detail and depth, and usually offers vertical movement to boot. The developers didn't skimp on the game play either. Not only is it easy to command your team, Vegas is designed to let you design certain encounters on the fly. Anytime you need to breach a room or take an objective, some simple tools let you designate targets and attack each target simultaneously. For those times when you have to rely on good old pin and flank tactics, you can take cover behind whatever item you'd like. Borrowing the idea from earlier titles like Kill.switch (horrible game but incredible use of cover), Rainbow Six Vegas makes it necessary but also very easy to take cover wherever you like. This highlights one of Vegas' only flaws though. Sometimes the game doesn't always pick your position that well, so you've got to be careful how you control your character.
Special attention should be paid to Rainbow Six Vegas multiplayer. Although it is reportedly a tad buggy, especially with the audio, it does offer a wide variety of game and character options, and stands up as reputedly 'awesome'.
Oh, one thing I forgot to mention. The single player storyline in this game rocks. Vegas is awesome, especially when you're storming it with an MP5.