The game Mercenaries is a lot of fun.
You're pretty much a one man army, who can take a lot of bullets, but it is very hard.
You can drive tanks, helicopters, or just shoot the crap out of things yourself in 3rd person. You also have various options of laser guided air strikes, bombing guided by satellite or calling in artillery support from outside the map. At first the game didn't impress me much, but after the couple of early missions it turns out to be a great game.
Not as tactical as a rainbow six though.