In order:
1.) Mosin Nagant M44 -- gotta have the bayonet, and I love the KA-FARGING-BLAM, and three feet of muzzle flash that causes the ground to shake, the grass to catch on fire and the guys next to me pee their pants.
2.) AR-15, very accurate, easy to shoot, just an all-round nice gun
3.) No4 Mk1* Lee Enfield -- it's hard not to do "mad minutes" with this thing! Very accurate, very fast cycling, heavy, and still has plenty of bark.
4.) AKM -- WASR AK-47, light (lighter than an AR), handy, good bark, good bite, and accurate (I handload).