Wow, I can't believe nobody thought of this...a GE M134, ya know? the .308 sized 'mini' gun, and a Glock 18 suppressed. Why not go all out 'Action Movie' mode?
Assuming we had this hypothetical tyranny, and to be more smart with my choices instead of picking the funnest, I'd actually go with a Cobb MCR (Multi Caliber Rifle) for the rifle. Not only can the barrel and upper receiver be swapped out for all the AR-15 length calibers, the magazine well is a modular section. I'll start with having it in 9mm, 5.56, .308, .30-06something in the 338-416 range, and .50 BMG. For the pistol, the best handgun I ever fired was my dad's Sig 226, assuming I can't get anything NFA restricted, which is how it is in my state already.