Tequila Sunrise
Adventurer
It's funny you mention half-orcs, because I don't like them. Or rather, I don't like that half-orcs are playable but orcs aren't. So in my games I call them 'orcs' and move on.Several people have mentioned that they are ok with restrictions as long as it is not arbitrary. So I'm wondering, as a player, why would this bother you?
Anyway, speaking for myself, arbitrary restrictions are...potential pitfalls. For example, I have a thing for dual-wielding characters. And in D&D, that means Str and Dex. In 4e, half-orcs are one of the few (only?) Str/Dex races so I might be bummed if my DM took half-orc off the table. (This is why I advocate floating racial boosts.) Of course, another player might like half-orcs because of the racial theme, and be bummed for a similar reason.
That said, occasional arbitrary restrictions aren't a big deal. I can just play a different character. It's when a DM has so many arbitrary restrictions that a first-session conversation goes like "I'd like to play A...no? Okay, I've had this other character idea for a while...no? Alright, how about...no?!" That I'd start looking for the door. Which I've never had to do.
The most restrictive DM I experienced wouldn't okay the 3.5 scout class -- because the skirmish feature isn't "realistic," which I think is pretty arbitrary in a game where rogues can dodge 1/day and roll extra will saves because any ability with "slippery" in the title apparently fits the rogue theme. Nevertheless, I found an acceptable character to play.
I'd never play a character I just wasn't interested in though, no matter how interesting the DM's campaign is. There's compromise, and then there's "I might as well be picking a Diablo toon."