I don't eat meat or fish for ethical reasons. This includes anything that could be classed as a corpse, i.e. red meat, white meat, birds, fish, seafood or insects, and other parts of corpses like lard and suet. I don't eat gelatine because it is also dead thing, but as I can't avoid it in medication (the choice is between taking pills that keep me sane or the same drug in a non-extended release form that makes me have ultra-rapid-cycling manic-depression) I will very rarely break down and eat non-vegetarian jelly sweets. Don't hate me for that.
I don't particularly mind people eating meat near me, but I am severely squicked by any meat product that still looks significantly like the animal it was when it was alive. This includes most seafood and those tiny chickens (poussin?). Heads are bad. Tentacles are worse. And I once almost had a minor nervous breakdown in a restaurant when a lobster was dismembered on the table in front of me.
I don't eat dairy for health reasons - am severely lactose intolerant and taking lactase enzyme doesn't actually help. Small amounts of butter and very small amounts of cheese might be ok, but I can only eat them once every 2-3 weeks, if that. To be honest, my tolerance to dairy has been gradually diminishing over the past few years, and it's getting to the point now where a) I've got used to non-dairy replacements and b) I'm not sure I can be bothered to deal with the consequences of eating a pizza. Likewise, I discovered a few months ago that egg was a major trigger for IBS, so since then I've been basically vegan. But I can cope with small quantities of egg buried in things (like pasta).
Other triggers for IBS are sulfurous, excessively fibrous or acidic fruit/vegetables. I can't eat sulfurous vegetables like spinach or green cabbage (or brussels sprouts - but they're vile anyway!) At All but am ok with smallish quantities of white & red cabbage, lettuce, broccoli and crispy "seaweed" (i.e. fried to death green cabbage). Have to be careful with alliums (onion, leek and garlic), but they are easy enough to identify & pick out of food if necessary, and I never have problems with garlic bread anyway.
I am not in any way shape or form allergic or intolerant to aubergine (eggplant), but I don't seem to like it, and would rather it didn't feature in my diet. Don't care hugely for mushrooms for slightly complicated reasons, but quite like mushroom chopped up & buried in things like spring rolls & gyoza. Although scary black shiitake mushrooms trigger my "not food" reflex quite badly.
Then the part that makes everyone think I'm a health freak: I don't drink anything containing caffeine or alcohol. I am wildly hypersensitive to caffeine - in small doses it gives me weird loopy acid trips and in large doses migraine and fits. I know it's not psychosomatic, because when Dr Pepper first became available again here after years of not, I didn't know it had caffeine in, and drank half a baby can (one of those 150ml pick'n'mix cans), and had the disorienting experience of being completely stoned in the middle of a shopping centre and not knowing why. Chocolate doesn't seem to count as a caffeine-containing chemical, or at least, it doesn't have the same effect that tea, coffee, Coke and Dr Pepper all have. When people learn I don't drink caffeine they always offer me decaffeinated tea or coffee, but because I've always been hypersensitive to caffeine, I never learned to like the taste of tea or coffee. Sorry.
I am only "quite" sensitive to alcohol - I don't drink it simply because I don't get the pleasant giddy drunk feeling that most people get. 1/4 unit of alcohol is enough to push me straight into the depressed self-loathing stage, plus I will feel violently sick and be scared because I'll know I'm too drunk to look after myself. Not recommended.
I don't know whether the caffeine thing counts as an allergy - I usually count it as one, because it is severely contraindicated, whether it provokes an actual immune system response or not. I am also mildly allergic to casein (milk protein), which is handy as I have to avoid dairy for lactose reasons anyway. I am definitely allergic to melon, and I might be allergic to strawberries (but I can apparently eat strawberry jam without distress, as of yesterday).
Now for what I do eat. The "don't eat" list seems really insane, so I should probably mention foods I do eat.
Soya is good - anything made from soy is good, including edamame, tofu, miso, soy milk, soya fake meats... :) I like most fake meats - tofu in most forms except plain boiled (just boiled it's The Blandest Thing On The Menu, too bland even for me!); soya, wheat or pea protein burgers & sausages; seitan if you can get it & know how to cook it... The only thing is, fake meat with a strong "meaty" flavour makes me feel sick.
Most soy milks are pretty disgusting imo, and taste far too much like porridge, but I like Alpro Soya (UK & Europe) and Silk (US) - those are the soy milks I'd buy if I wanted to eat breakfast cereal where you can actually taste the milk. Otherwise, if I'm burying it in chocolate, any old soy milk will do. But it needs to be calcium-enriched.
(Please note that vegan fake cheeses are SCARY and the only one I've ever met so far that I'd touch with a bargepole is the one that Pizza Pi in Seattle uses on their pizzas. This doesn't help you much, does it? I've tried making vegan cheesy sauce with nutritional yeast and cashew nuts, but it was a bit... "interesting".)
Pulses and nuts are good - I am miraculously not allergic to any kind of nuts (the cynic in me adds... yet) and love love love cashew nuts and sweet smooth American-style peanut butter. I do however believe that most nuts are savoury food and am somewhat confused by walnuts and pecans in cakes. I really like falafel, and have recently started enjoying hummus too. Show me a good place to get falafel (like Maoz!) and I'll be your friend for life.
Carbohydrate foods are good: rice, pasta, potatoes (I LOVE potatoes), cereals, bread...I'd say I never met a carbohydrate I didn't like, but there was what Richard & I term The Quinoa Incident, and black rye bread scares me... My idea of a good meal is an Indian where I get poppadoms with mango chutney, potato and cashew nut curry, plain boiled rice, chapattis or pooris, lentil dhal and/or chana aloo (chickpea), and a big fluffy naan bread stuffed with vegetables. In other words, carbohydrate, carbohydrate, carbohydrate, carbohydrate, protein and carbohydrate. Any meal with 5 sorts of carbohydrate can't be bad :) I also rather like roast potatoes with pizza, and pasta with chips. Or roast potatoes, pizza and pasta as a single meal (mmm).
Fruit & vegetables are good, if a little obvious.
Cooked Chinese & Japanese foods are positively fantastic (anything featuring fried tofu + one or more carbohydrates HAS to be good), and you never know, someone who makes sushi for me while the rice is still warm might be able to get me to like it. But sushi out of a fridge is just ick, especially the wasabi and (real) seaweed.
I adore cakes & puddings of any kind but avoiding dairy in desserts gets tricky and fruit salad annoys me by being too damn obvious (what do vegans eat? Vegetables!). Sorbets made without milk protein should be easy to find, but frequently aren't (why does whey powder need to go in everything?). Dairy-free chocolate cake and mousse or dairy-free ice creams are my absolute favourite, but a pain in the ass to find unless you know where to buy the ingredients.
The two main makes of dairy-free ice cream are Tofutti (produced in the US) and Swedish Glace (European, but imported by American companies like Perry's). They are both soya based. Tofutti is dairy-free but technically not vegetarian simply because the sugar is processed using animal bone charcoal. However virtually all cane sugar in the US is processed this way, so it's almost impossible to avoid, and I eat Tofutti occasionally. Swedish Glace is 100% vegan and also 100% delicious, although I reserve judgement on the Caramel and Mocha flavours (there's something so wrong about polluting delicious chocolate with vile coffee). You can also get oat ice cream called First Glace, and the company make some lovely dairy-free Magnum-alikes called Supreme, which some large branches of Sainsbury's carry.
And I've linked to them at least three times in the past year, but montezuma's - for all your vegan chocolate needs. (They do LOTS of dairy stuff as well).
Am exhausted now! Feel free to ask any questions (though I reserve the right not to answer them).