I'd go with the MP5 in this particular situation, but I would prefer an MP5/10. The G3 is tempting, but if the rest if the security force is down I'd want more than 20 rds and burst capability. Also, a suppressor system would be a nice bonus if logistics permit.
+1 H&K military weapons if you can get your hands on them.
You can have your churches, I'll keep my guns. Just keep your hands off my paycheck and your eyes out of my backyard.
Join the Libertarian Party! http://www.lp.org