Call of Duty:Modern Warfare 2

I like that red bldg that's right near where wyndellmac is talking about. It's got a window that looks out over the grassy area by the bridge. It's got access to the sniper windows Twenty was talking about.

Only problem is that it's highly trafficked. You can get a bunch of kills, but you need to stay lively. It's a tight spot so being grenaded can be dangerous, but you're guaranteed lots of action.