I did post this on another profile, but I've abandoned that one, so I'm posting on my real one.
This is obviously the Halo Magnum in its real life proportions. It is a little under an inch longer than it should be, but otherwise almost perfectly accurate.
About this creation
It has a moving hammer that snaps back without breaking. It has a removable mag (no ejection mechanism, but it is easy to take out and replace) and a moving trigger.
If you want it, I'm selling it for $250 on Bricklink, but that is easily negotiable. http://www.bricklink.com/store.asp?p=DoctorFaust
Wow, I'm surprised this isn't more popular it looks really accurate. I always liked the pistol in Halo CE, but after that they toned it down to much. Good job on the moving parts, that is hard to do while still making it look right.