As a parent of a 5 year-old daughter, I have tried just about every stain remover out there. The hands-down winner and champ is Ickee Stickee Unstuck. I was given a 4-ounce sample bottle and it has lasted 6-months. It is the industrial strength version of all the orange-based cleaners and works better than everything else, even the previously reviewed GooGone. (I was always a fan of GooGone, but this works even better as it seems to penetrate the sticker where goo-gone seems to want to seep under the sides).
Among other things, it has easily taken years old sharpie off of white melamine, removed supposedly water washable marker stains (you know the brand) off of painted surfaces that magic erasers just removed paint from. It has taken my best paint brush that got left out and encrusted with latex paint back to usable condition. Not only that but it can be used diluted and still works great, and is 100% biodegradable as it is made out of soy.
Yes, I am the same person that sent in my raves to the company whose testimonials and photos are plastered all over their site. The stuff is so great I just had to share, and I admit I went full-on Billy Mays for a while after my kitchen cabinets went back to white. I would tell you everything I cleaned, but part of the fun is seeing if there is anything it can’t clean.
[Note: This product is manufactured by Franmar Chemical, who produces the previously reviewed Soy Gel Paint and Urethane Remover. Ickee Stickee Unstuck is also a soy-based solvent, and outside of being a general purpose cleaner, it appears it is predominantly used to clean silk-screening pallets and stubborn ink stains in industrial settings. -- OH]
Note: After working in a machine shop I learned the value of having a Material Safety and Data (MSD) sheet on hand in case of an accident, so for those interested here is a link to Ickee Stickee Unstuck's MSD sheet (PDF).