Ketchup (certain brands contain gluten)
Ice Cream (Some companies use wheat by products as a stabilizer)
Beer Personally, I don't drink and hate the smell...and I guess most people know it's made from barley.
Grocery-store 'brand' foods (these brands are often produced in facility that makes everything! Which means lots and lots of cross contamination with the equipment or stray bits here and there. Check your cheese, dried fruits, nuts, everything to see if it says "May contain wheat" or "Made in a facility that also processes wheat".
Fast Food French Fries (through cross contamination. Be sure to ask if they use a designated frier and if their fries are gluten free.)
Medicines and medications (Check with your pharmacy, doctor or read the ingredients).
Your shampoo, lotion, etc... (I found that even my skin is sensitive to gluten and some of these may irritate yours as well).
Accidents are going to happen, let's face it. But each needless time we get 'glutened' that's another two weeks of 'immuno-warpath' on the the old intestines. Better to watch out.
For more help on avoiding the wrong foods, try these links: