If we are talking "survival" (not against humans/zombies) and "1" really means "1" (i.e. no extra conversion kits, extra fixed, folder, camp, fighter, ect) AND I have to carry them...AND the stuff to feed it, then:
Rifle: Ruger 10/22
Pistol:Browning Buckmark
Knife:Battle Rat
If "urban" (human/zombie targets) and I know I will be able to supplement with other stuff then: