-
35mm Smena cameras are cheap enough have decent glass and don't have anything to stop you cocking the shutter on an un-advanced (or partially advanced) frame.
If you want a bit more control and image quality etc, some cheapo SLRs also have a little button you can press to disengage film advance and frame counter. (i.e. you just press it whilst pulling advance lever and it cocks the shutter without moving film) - I bought a Chinon CG-5 with 50mm lens for £2 on ebay that had this handy feature
Best (easiest) cameras for double exposures?