Although I had a recent run-in with a lobster, and some clam chowder, I have been a vegetarian for about 17 years (starting at age 11), and in all of those years I have come up with a list of my least favorite attempts to accommodate vegetarians. So in no particular order, here goes:
1) The salad bar:
This was often my alternative in some fast food restaurants and middle-brow chain restaurants as in TGIFridays, Max & Erma's, etc. It generally lead to a belly full of ice-berg lettuce and chow-mein noodles, and some mass produced chocolate pudding. I have to say that after years of consuming this is I was thoroughly anti-salad. This has changed only in the last few years. Unfortunately, most mass produced food outlets put chicken or a panoply of meats on their salads, so I've rarely had to test my mettle whilst away from home on a sustained salad diet.
2) Hummus and Roasted Red Peppers:
I've generally very much enjoyed Lebanese/Mediterranean inspired foods in general (falafel generally remains in my top ten, particular in its Sudanese or Syrian variants), but the prevalence of this particular item in delis, bagel shops, and departmental events as the only two-birds-with-one-stone vegan/vegetarian option pretty much makes my stomach turn now. Especially because the slimy red peppers are either half-frozen, or just greasy. Roasted red peppers stiffen my resolve on the fact that the only reason peppers exist are to be spicy. Without this raison d'être, I can't see why peppers should maintain their expensive existence.
3) The Portabella
I am not altogether sick of this alternative, but at BBQs this has been proffered by sensitive folks for vegetarians, usually marinated in olive-oil and wine. That mushrooms could be understood to replace the protein and flavor of meat has always surprised me.
4) Morning Star Farms Veggie-Burgers:
With the consistency and flavor of a kitchen sponge these are proffered often when invited over to dinner, and the host has either forgotten you are vegetarian or lacks the imagination to make something not steeped in a meat stock of some sort. Generally these are pulled out the "tisk tisking" like observation of "I don't know how you get enough nutrition on that diet."
Tomato soup tastes like bile. Cold, greasy and flavored this characteristic of tomato soup is only amplified.
6) Baked Potatoes:
These are another fast food favorite usually dried out from being in the oven too long with a dollop of sour cream and dried out chives. I haven't had one in years.
7) Beans and Rice:
Left-over from the days where the "incomplete proteins" myth reigned supreme, I actually still like these, but actually cooked. I am fucking Mexican and I know how these things should taste, so a bowl of boiled rice and kidney beans with salt would not and should not "cut it." Moreover, the beans should always be black. Here is a recipe that is passable.
8) Boiled Buckwheat:
This really only occurred in my undergraduate institution, in my few limited years as a vegan. But the flavor of buckwheat on its own is one of the more unpleasant food flavors I've ever encountered. Needless to say I lost weight in college despite the weekly beer deposits.
9) Uncooked silken tofu:
Silken tofu is usually produced to make sauces and pudding like substances. It is not a salad topping or good idea for casserole dishes.
For some reason my grandparents thought fish were biologically vegetables for a long time. I tend to regard the flavor of anything that tastes like the environment it lived in, i.e. a river or ocean, to be rather nauseous, so naturally this was not my favorite non-alternative.