J.C.
My son was this way and another mom mentioned having them take "thank-you bites." What we do is if I know I'm making something he doesn't like, I'll make something else (like frozen chicken nuggets) but if it's a situation where he just doesn't want to eat it, he has to eat 1 bite less than his age. It stops at 10-so he's 4 now and he has to eat 3 thank you bites, which is thanking me for the meal I've made. Only if he eats a "good" amount can he have dessert, but if he eats his thank you bites he's allowed to get down and have nothing else for the rest of the evening (or if it's lunch, until dinner). He was doing much better with only having to eat 3 thank you bites (we started it when he was 3, so then he only had to eat 2) and he started being willing to eat more as far as amount and variety. If I make something I know he doesn't like, about every 3rd or 4th time I make him try it, and he's actually started eating some of those as well. It's made mealtimes much more pleasant for us! He still takes forever to eat, and is still picky, but it's gotten a LOT better.