#1 something in 308/30-06. I would love the M14 if money was not an issue.

#2 12ga pump or O/U. Not picky as long as it works and is reliable.

#3 Reliable handgun in a popular caliber. G19 would be a good choice. It's reliable and there will be many like it floating around in case you get desperate and need to trade off mags/parts or if you need to trade for mags/ammo/parts.

It seems the three gun combo is rifle/shottie/handgun. More important the semantics of revolver vs. semi or pump vs. O/U is keeping them in popular calibers. This gives more options to trade or scavenge ammo and parts.