Dalek Caan said:
Being able to fire a M1 Garand would be pretty cool.
I've got an uncle who collects WWI, WWII, and Korean War firearms, and the M1 Garand is his personal favorite. He has like twenty of them now, including a rare M1-E5 "Tanker Garand" (18" barrel and collapsible stock variant that never entered service which was meant for paratroopers and vehicle crews), an M1-C sniper variant, and two M1-D sniper variants.
His pride and joy though is a standard M1 Garand that was sent to the British as part of the Lend-Lease program and was left in a locker and forgotten until after the war. It was manufactured in 1940, still has all of its original parts, and has never been fired.
They're a lot of fun to fire, and actually make for a pretty good choice for beginners. Just gotta watch out for M1-Thumb. If you're not careful, they bite!
EDIT:
As for me? Probably a Mk.19.
I've got a friend who was a combat engineer in the Army Airborne that speaks fondly of getting the opportunity to fire one mounted on one of his unit's Humvees. It's a belt-fed automatic 40mm grenade launcher.