I have a few "standard" recipes up my sleeve for the restrictions I deal with regularly - GF, CF and vegan. I'll try to accommodate. Nobody's ever requested halal, kosher, nut-free or any of the other things listed - nut-free would make me VERY nervous, but I'd obviously try to accommodate. I'd probably serve very simple foods in that case, like hard-boiled eggs and crudites, that are hard to screw up. :p
What does annoy me a wee bit is when people cheat. My supposedly dairy-free friend comes over sometimes, and I'll always try to make her dairy-free food (or with minimal dairy, it isn't a hugely severe allergy so traces of milk in the garlic salt or whatever is fine). For mains, it's not such an issue - I'll make a cheese sauceless, cheeseless mini-lasagna as well as the big cheesy one for everyone else. Desserts are more of a problem, but I have an ice cream maker, so I'll often do something like mango sorbet. But then she'll turn up and say "Oh, it looks so yummy, I'll just suffer later!" and eat the cheesy lasagna and the chocolate mousse anyway. Which means a lot of wasted effort.... but I don't like to ignore the CF issue next time, in case she's feeling less free and easy, you know?
My "vegan" sister does the same thing. It's actually quite a pain for me to cook vegan, because I'm a TFer and actually try to get animal products in dishes wherever possible. So I usually cook rice in chicken stock, and now it tastes bland and boring to me if I don't - or I'll fry potatoes in chicken fat, or use butter to soften onions, or whatever. Obviously I CAN vegan-ify it, but it tends to make an inferior dish IMO. So it annoys me greatly when I do all that, and then after the meal see her happily munching on cookies I made with butter and eggs, or helping herself to frozen yoghurt, or whatever. That strikes me as pickiness rather than ethics, and I have much less sympathy for it. Particularly because she's my sister. :p