1. HK Mark 23
A .45 caliber handgun designed specially for use by U.S. Special Forces. One of my favorites.
2. Colt 1911
Another .45. It used to be the the official sidearm of the U.S. army from at least WWII through Vietnam (don't quote me on that). I believe it was replaced by the Beretta M9 9mm.
3. HK USP
Appears to be created alongside the Mark 23 and for the same purpose. Can be chambered in .40 S&W, 9mm or .45.
A carbine derived from the M16 assault rifles currently in use by the U.S. military.
It can be chambered in .223 or 5.56 ammo.
5. Desert Eagle
Not sure if there is a technical definition of a hand canon, but I'm guessing this would be one, if it is. It was developed by the Israel Military Industry (IMI) and can be chambered in .357, .44 Magnum or .50 Action Express. Fired one with .357 before, wouldn't checking out the .50 version sometime.
6. Jericho 941
Also developed by IMI, this is much smaller than the Desert eagle. It's chambered in 9mm, and sometimes called a Baby Eagle.
7. HK MP5
A submachine gun chambered in either 9mm, .40 S&W or 10 mm. I believe it was banned in the 1994 Federal Assault Rifles Ban, so it might be hard if not impossible to find. They are (recently, I believe) released a similar gun (at least aesthetically) chambered in .22 LR, but it just wouldn't be the same.
8. Colt Single Action Army
It is the classic Wild West gun. If you have ever seen a Western, somebody was probably using one of these. A friend of mine has it chambered in .22, I'd like to have one in .45 Long Colt.
9. Winchester Model 1894 Lever Action Rifle
Again, another rifle you would have seen if you watch the occasional Western.
10. Mauser C96 "Broomhandle"
The pistol used to create Han Solo's blaster in star Wars. Enough said.
11. Beretta 93R
I like Beretta's pistols, mainly the 92 series (I already have a 92 variant, so I didn't want to put it on the list). This is, essentially, a Beretta 92 9mm pistol but with 3-round burst fire capabilities (i.e. one trigger pull=three bullets fired) to help control the muzzle burst it comes with a muzzle brake, a forward grip, a detatchable stock and a 20-round magazine. I don't think it is produced anymore, I just like the idea of firing a machine pistol like this.
12. FN P90
A submachine gun chambered in 5.7 mm. Like the HK MP5 listed earlier, it was banned in '94 but has reappeared in .22 LR form. again, a .22 would just not be as much fun.
13. Hand-Held M134 Minigun
Just had to add one of these to the list, because it would be a whole lot fun to fire something like this. This is the kind of weapon you'd see mounted on a helicopter, but a hand-held version was seen in Terminator 2 and in Predator. In real life, something like this would have to be mounted, I doubt that anyone could control this thing firing from the hip like they did.