I'd start with one of the Purple Power, Simple Green type cleaners. These are relatively cheap and can be used for other things around the house if they don't work for paint removal. They can be poured down the drain when finished. Caution, use surgical type gloves. It actually begins to dissolve the fat in your skin making your hands feel oily and look like prunes! The active ingredient in this stuff is found in anti-freezes and............."Solvaset"!
Others:
Brake fluid- Very nasty, messy, oily. You will then probably have to use one of the above cleaners to remove the oil. Has to be disposed of properly. Not the drain!!
Drain cleaners- Very caustic. Its a strong "base" the opposite of an "acid" but can be just as nasty. Aka "lye" potassium or sodium hydroxide.
Oven cleaners- see drain cleaners. Comes in an aerosol spray can. Comes out as a foam. Use in a well ventilated area. The mist from this stuff will get into your eyes and nose/mouth.