1) Loki A - the wildcard. An odd choice I know, but think of it this way. 2 Large beam lasers with souped up clan goodness for cutting through hordes of undead, destroying barricades, digging massed graves and dealing with pesky government forces.
2UAC5's, when sometimes you just have too many zombies for those lasers to cope with, you need some 480RPM exploding corposes Autocannon goodnes. Worried about a horde? no problem, cut it apart in seconds. Worried about a super zombie? no problem, nothing is going to survive being hit be a couple of UAC5 rounds and not get ripped apart. 2 tons of free ammo means 1600 rounds per gun. Whats not to like?
Finally, 2 Machineguns for backup weaponry, when you just don't feel like wasting the effort/resources of using your larger weapons, and an LRM15 for some long range area bombardment. (need to infiltrate and over run army base for supplies? no problem, smoother the area in firey death first). Also, coupled with 86kph on land (faster than any zombie!), and a Beagle Active Probe (for locating survivors, food stashes, and anything else an advanced sensor package might be able to pick up in a zombie apocolypse)
Whats not to like?
