double barrel 12 gauge. never jam, most common ammo for a shotgun, cheap and easy to use. i'd have a .22 pistol on my side with as many bullets that'll fit in the mag if the my boomstick fails (yeah right) or i can't reload in time. that's for the real zombies, as in fast as molasses.

if they're sprinting everywhere which seems to be the new cool thing in undead flicks, i'd have a striker street sweeper and a glock 18c. not for the full auto but the fact it's 9mm and had a 30 round mag.