My list is long and probably not complete (I had a tenth item a moment ago, then promptly forgot it), but here goes, in no particular order,
Finance restrictions:
1) Paid DLC, or much DLC at all - I guess I'm from the age where you bought a game and you had the complete game. Though I'll often use DLC if it comes free in, say, a "complete" version of a game, I'm not that fond of the idea in general, and often won't install even free (or free to me, as with a new game purchase) DLC. Non-cosmetic DLC usually throws whatever balance the game had out of whack, and cosmetic DLC I can easily live without.
2) Mandatory Internet connection in a disk game - If I buy a digital game through Steam or wherever, I expect to require an Internet connection to get the game working at some point. But if I'm buying a disk, the game better be installable and playable right out of the box, without any Internet connection required.
3) Monthly fees - Haha, no. I will pay you once for your game, and then never again. I might, if I liked your game, buy its sequel or expansion or whatever, but I won't pay you on a recurring basis, ever.
Design restrictions:
4) First-person viewpoint - I respect the design choice, but I get lost way too easily in these games. I can keep a 2D map in my head, and usually I'm pretty good at knowing what's in which direction in real life, but I tend to get hopelessly lost in these games, and running around in circles is no fun, especially if I'm not sure if I'm in a new area or if I'm seeing generic corridor #1457 for the umpteenth time.
5) Realistic violence - I like my enemies to disappear when I kill them, or break up into a collection of polygons, or something like that. I do not like them to leave a corpse. I do not like blood effects in my games. I can bear with it as long as I'm not killing them with a real weapon -- maybe I'm throwing a fireball or something -- but killing even virtual baddies with knives and guns kind of gives me the creeps.
6) Too many choices - this one may need some explaining, since oftentimes choices are good. But I tend to get stuck with options paralysis if the choices are of a permanent nature, and since I only play a few games through multiple times, each choice usually just means more of the game that I'll never get to see.
Story restrictions:
7) No story - Unless your game's like Mario Kart or NBA Jam or something, I want a reasonable explanation for what's going on. Heck, I usually want this even in games like Mario Kart and NBA Jam. Very few games have sufficiently engaging gameplay to keep me going without at least a little bit of plot tying it together.
8) Unreasonable choices - false dichotomy - Too many games seem to offer a "be a saint/be a sociopath" false dichotomy. What if I neither want to forgive the big bad nor murder him in cold blood? Sometimes there's a neutral choice thrown in. It doesn't always help.
9) Unreasonable choices - unrealistic choices - I'm fine with being able to pick my character's class, but I don't much like being able to pick gender, race, height, etc. No one in real life gets to pick them, and I've found that "Play as male or female!" is shorthand for "Our story is terribly generic because we couldn't even guarantee whether the character we were writing was a boy or a girl!"
None of these is a deal-breaker by itself, except the monthly fees one, although any two of these is pretty much an immediate turn-off, and I don't think I've ever bought a game that had three or more, except maybe Dragon Age, which I thought was okay but not all that great.
