[Luger]

I would go with nail polish remover.
-Don't use too much and rub gently with a Q-Tip until the paint is gone.

-Once you've removed the paint make sure to clean the tip thoroughly with soap and water to make sure there is no solvent remaining on the gun.

-Krylon actually makes a "plastic paint", it is specially designed to bond to plastic. I have used it myself around the house and it works great.

-Let it cure for a day or so, and you won't have any problems with the paint peeling.

I know some of this info was already posted, but I just wanted to give my 2 cents.

Hope this helps!

P.S.- What movie is it for???