Right when you die, throw a grenade. You'll drop the grenade as you die and it just sit, lying on your dead body. When your killer gets ammo from you, he blows up. Sure it's a bit cheesy, but hey, if you were any good, you wouldn't be dead, would you?
Weapons that take a long time to reload can be reloaded faster if the next weapon button is pressed right after you start to reload. This basically starts reloading the next weapon right away, leaving the previous weapon loaded and ready for your shooting pleasure.