Tom Clancy's Ghost Recon is an excellent game by Ubi Soft depicting a war in the near future. The PS2 version has Desert Seige with it as well. The single player modes can seem a bit lifeless but playing deathmatches against your mates will never lose its fun. It has bucketloads of real weapons and good fun for any gun fanatic. The graphics can be a bit dodgy at times, e.g, watching someone about half a click away with a sniper; the animation isn't very fluid. Overall a great game, but more fun with friends.
I played Ghost Recon with my friend and kicked his ass.