This list may offer a few "watch out" products for people living gluten-free.
1) Tinned/Jarred Beetroot - Although you can buy different brands that do not have gluten, jarred beetroot will often be kept in vinegar that contains Barely. Be sure to always read the label and don't just presume that because it's a vegetable its GF!
2) Sushi - Sushi is just rice, meat and seaweed, a sushi restaurant would be someone's gluten-free dream, right? Wrong! Sushi often has soy sauce in which is made with fermented wheat. You can buy special gluten-free soy sauce however and make it yourself or take it to a restaurant with you. I would recommend Kikkoman naturally brewed Tamari gluten-free soy sauce.
3) Oats - This is the biggest mistake you can make if you're gluten-free! So many people think gluten is only in wheat, barley and rye and always forget that they should avoid oats. Oats are grown on the same land and in rotation with gluten-containing grains. Gluten grains possibly can grow within the oat crops if they're planted in the field the previous year, in which case the oats become contaminated with wheat, barley or rye. To be careful buy specified gluten-free oats.
4) Meatballs - another common myth is that all meat is gluten-free, meatballs however often have breadcrumbs/wheat as a binder to retain its shape.
5) Medication - I learnt this the hard way, I had taken travel sickness tablets to prevent myself being sick and afterwards read the label to find out they had wheat in, so I was sick anyway. It is important to always read the label because formulations can change in both food and medications.