I like my method best. No chance of damaging the cart and causing discoloration in the plastic. You can also use this method on labels so long as you are very gentle and careful
After removing said offensive sticker (this works for "normal stickers too), apply a piece of duct tape over the sticky area, rub a finger across to get it to stick to the adhesive on the cart, and pull it off (gently). Repeat a few times until all of the sticky residue is gone.
If the silver stuff isn't sticky just scrape it off with a finger nail until you've got enough sticky stuff to remove it with duct tape.
Using any kind of alchohol, peroxide, goo gone, and other substances on carts can leave a residue and/or discolor the plastic. Never a good idea. It may not show up immediately but in the long run you can see where stuff like that was used.
REMOVING MARKER: Wet a tooth brush and gently scrub the area. Wipe clean with a cotton ball.