this lvl 4 sentry would be my king of sentry's: a lvl 3 sentry gun, but a dispenser attached to it, so it can heal itself, instead of banging on the sentry all the time... but you can press the use button or somthing, to turn it off when you feel like crouching and hitting your sentry, but when it runs out of metal it just shuts down until it has full metal again