Anything we're not allergic to. So, almonds and sesame are all over. Apples, rice products, corn, sunflower seeds, etc.
We're very careful with eggs, dairy, pork, carrots, chamomile, echinacea, and tomatoes. DH is very careful with his oats. We keep the house free of mango, papaya, gluten (except for DH's three oat products), cashews/pistachios, hazelnuts, peanuts, aloe, lavender, and soy.
No doubledipping, ever . . . except when I wipe off a teaspoon after getting cinnamon and then dip it into the baking soda. That's it, so don't touch my baking soda if you have a cinnamon allergy. We go through a lot of spoons and knives and are good at wrist-flicking. Heck, I don't even close up my bread (Udi's, contains eggs) without washing hands first and then again. DS doesn't use the grate on the toaster oven, only things in pans.
And kiddo is always washing up because he eats a lot of cheese and fruit products colored with vegetable juice (often carrot or tomato instead of beet).