Soups/sauces thickened with flour, corn starch, etc.
Asian foods are definitely one for that -- beef in a sweet teriyaki or soy sauce, meat that's been dusted and fried, oyster sauce, curry with green beans. I've almost ordered Chinese food several times until I really think about it and how much there is to work around and it gets exhausting :P So much could be paleo but the sugar or thickeners or vegetable oils ruins it. I wish there was an easier way to paleo-ify foods like that.. but it's not as easy as "hold the rice".
Reminds me of first describing paleo to a friend and talking about eating lots of vegetables.. "oh that doesn't sound too hard, I love vegetables! Peas, corn, green beans, sure!"
I was craving something comforting and mac-n-cheese-like the other day while we passed the hot food bar section in Whole Foods. I saw cauliflower au gratin, which seemed like at least a reasonably paleo substitution.. but even then I had to work around the crust of breadcrumbs on the top.