For removing stickers, WD-40 works quite well. On glass, spray it around and on the sticker, let it soak for a few moments, then use a razor blade... as long as you keep the glass wet, the blade will not scratch the glass and the stickers will come off entirely. I think the WD-40 is also safe around vinyl as long as you don't leave it there to sit for long periods of time. It works very well at removing the gum residue after removing stickers from glass and painted surfaces.