I want a MAC-10. I'd prefer full-auto, but that's not going to be in my budget any time within the next ten years, so I'm going semi. Preferably open-bolt just for grins.
Plus if the world ever ends and the government collapses, I can say "FINALLY I can convert this!" and go to work. Assuming I know anything about it and have a working machine shop by that point.
In the meantime, it'd just be a fun little blaster and would get tossing in the safe the first time I could afford a real one with a happy switch.
I don't get why people say they're ugly; they look functional. Pure. Function. This is a gun that says "you are on the wrong end and I am about to screw you up the ass with thirty-three rounds in two seconds flat. Have a nice day. Bitch."
MAC's are horribly inaccurate in full-auto (adding a suppressor improves this somewhat, though), but in semi-auto they CAN be aimed accurately. They're also one of the quieter firearms when equipped with a suppressor. The SEALs still use 'em, so they've got to be worth keeping around for some reason, right?