I carried a M16A2, M16A3, a SAW, and a 1911 at one time or another when I was in the Army.
I was going to leave them out of the list, but if I had to include all guns that I've qualified with, and actually I've probably have more hands on time with and rounds downrange, to include even sharing a sleeping bag (get your minds out of the gutter) it would include:
M16A1-Made by GM Hydramatic Div. and I think one was a Colt
M16A2-All Colts except one made by FN in the 90's
M4A1-Colt. Got the first issued ones in 1993 and we rushed to qual with it before going to Somalia.
M24SWS-We just got these but I got out before we had a chance to take the Sniper training that ramped up back up in 1993. We conducted a 2 week quickie course meant as a train-up/familiarization but by no means Sniper Training. It was marksmanship only.
M21-Same as above and this is the one I took to Somalia along with the very fist issued M4's, and it had a cracked rear scope mount that I found out to be cracked on the plane ride over there and I knew I was having a hard time on my last day on the range the week before getting deployed! Great! 2 rifles that I had the least trigger time with and deployed within 3 weeks of getting both! I only took it out once and w/o a scope and un-zeroed iron sights that we were told not to worry about b/c we won't use them!
M203-Grenade Launcher
M60-AKA "The Pig"
M249 SAW - I remember having to run qual ranges for other non-infantry units that never sent enough shooters. Lots of extra ammo to burn! I have a total dumbass on my part ND story with this one during GW-Desert Shield part. First off, it was pointed in the right direction - Iraq. And I was a Squad Leader and not a dedicated SAW gunner. However I am extremely familiar with the SAW having been a SAW gunner before and I was bored. I just cleaned it and had the bolt locked to the rear (fires open bolt). Well we leave it with the ammo belt in the feed tray, bolt foward since you can just cock it back from there and fire away. Unlike the M60 where you can't. So in goes the belt, closed the cover, grabbed the handle, pulled the trigger, and RODE the bolt foward until - BRRAPPP!! Oops! NO ONE HEARD IT! Except for me and my SAW gunner that we shared a "fox hole" as in fighting position. And I wasn't asking either. It was loud!
M2HB .50 cal MG-Ma Deuce=fun. Until you have to dismount

These old bitches will run on 30W oil as lube. And operating springs will darn near go through 2 sheets of drywall if you take that back plate/trigger off with the bolt to the rear. And no it wasn't me that did that.
M1911A1-Old beater! Probably the oldest gun I carried in the field. Only qualed 2 times with it and had the old leather chest rig for M113 driver's only.
M9-Beretta 9mm
M242 Bushmaster 25mm chaingun- Bradley gun. And I thought dismounting a 50 cal was a PITA until we had to do these for maintenance purposes only! These things are a huge PITA!
M240C -coax MG on a Bradley
Besides those, tossed a few grenades, shot 5 M72 LAW's, 2 AT4's, one M47 Dragon that broke it's wire, and my gunner got to fire one TOW when we qualed on the Bradley systems.
HK G33, G3, HK21, a genuine L1A1, L85A1/SA80, FAMAS, AUG during a 3 day long NATO Infantry Day in Belgium 1986. They shot ours and we shot theirs. They had other weapons we got to check out but those are the only ones we got to familiarize with. Also Schuetzen thingy that I didn't get.
Remington 870 - still qualing with every quarter.
HK MP5 - 1 half ass qual and a MANY familiarizations. There is a story involving a fellow officer/SWAT member, an MP5, a dying cat, a city dump, and a call of SMG fire at 3 am.
HK UMP - still qual every quarter.
Oh, and I forgot, a Glock 17
I can't believe I forgot about shooting a Mk19mod3, auto grenade laucher. 2200 meters HE fun!!!! I only got to live fire it once, 80 rounds. That was when I was with 9th Inf Div when they were motorized infantry, i.e. rat patrol.
In 1987 I witnessed a mishap. When splitting up the ammo someone dropped a belt of 40mm grenades and the corner of the ammo box hit a primer. The ammo area/box was surrounded with about 6 soldiers. They all turned and began to run as the belt fell then a really loud bang. One guy got a piece of casing in his leg and the warhead travelled about 10 meters hiting a guy square in the chest and carrying a couple of belts of 40mm. We all wore kevlar vests and helmets of course. The round hit him and dropped on the ground. Grenade warheads has to travel 31 meters, spinning, before arming. No telling how many times that thing spun and I dont remember how many spins in 31 meters, but at that point it doesn't matter. The guy that got hit with the warhead said it felt like a solid punch in the chest, but remember it was a free flying round.