AQ2 was nice, because
- no respawn while a round was active
- hit zones (head = bad, legs could break)
- bleeding (you need to bandage yourself, sometimes _fast_)
- instant kills were possible with ~all~ weapons. Standard pistol to head, one shot. Throwing knives (My favorite!) to head -> Dead. Knife to stomach? Chuckle, run - he's going to bleed to death w/ a 80% chance.
- equipment/weapon selection at the start of the round a la 'classes', but more free. Giving you stealth (no footstep noises), protection (armored vest), better/more weapons/ammo etc.
- nice variety of missions and settings