I'm dating myself with my nomination:
1973
Day of the Jackal
The custom made sniper rifle that fit into a cane.
Looking fwd to hearing about your favorite "movie weapon".
Jimbo
My favorite not so realistic gun is the double Desert Eagle from The Green Hornet.
For more normal guns it has to be the Beretta 92 that is in many movies but it really caught my eye in The Boondock Saints. When I saw it in that movie I had to have one. I love it....
Funny thing is that I was just reading on IMFDB that in some scenes the double Desert Eagle is just a Beretta 92 with a slide on each side of the 92's slide.
Jack Bauer's HK USP9! It has capacity measured in crap tons. Magazines are obviously light enough to carry 30 or more. It becomes accurate as a death ray if you close one eye. And, when empty, it's polymer frame will knock someone out faster than slamming them over the head with a fire extinguisher!
I've always been a fan of the Barrett 50cal. many movies have it, the "Shooter" for example.
Another one is the Vector SMG from the new Resident Evil movie. I held it in real life and I was sold! Dual-wield Vectors would be the sweetest! Takes 30rd Glock mags and has virtually no recoil