Miniguns

" It's like a chainsaw that spits bullets." -- Jesse "The Body" Ventura

7.62 mm bullets to be exact. This is the manpackable version of this area suppression weapon. With a cyclic rate in excess of 4000 rounds per minute, this is just the kind of tool you need for the point defense of your bunker. You might not be making 100% head shots, but it's sure to slow down the shambling hordes one way or another...