I'm quite the picky eater as well. But it's rarely due to the taste. It's the texture, that I'm very particular about.
My grandmother used to make us (her grandchildren) these classic Scandinavian meatballs, which of course contained onions for flavour, but I refused to eat them, because of my disliking for the texture of the roughly chopped onions, so she hap to mash them for me.
As many of you've also mentioned, I don't get tired of the same foods either. I've been eating whole grain buns with peanutbutter and banana for the past couple of years. Still tastes well.
I became a vegetarian at 13/14, which forced me to try out all sorts of new foods, which helped me in the picky aspect.
Some types of food still really bother me; the spicy ones (I become strangely overstimulated and frustrated), mushrooms (unless they're mashed and stuffed into my nutroast), liquids with too much flavour (I only drank water and milk though my entire childhood - these days I also manage to drink apple juice once in a while), deep fried food, thick sauces, "heavy" dishes, salty food, boiled eggs and so much more.