This isn't supposed to be just a list of insults per se---these are phrases or words that started out as ethnic insults but became applicable to people in general. (Some people have suggested kike, wop, etc., but as far as I know these never became applicable outside particular ethnic groups).
indian-giver Even as a child, I wondered whether this is supposed to be ironic---after all, it's the whites who "gave" land to the Indians, only to take it back later. I'm pleased to see that several lawsuits have upheld some of these treaties (and the treaties aren't all that old...often less than 120 years!), to the consternation of some who think that it'll be just terrible if the country actually honors its word to the indians...hell, if this keeps up, they'll end up owning the whole damn country!
you're a Philistine A little research is in order, as I'm ashamed to admit that I don't know who the Philistines were...though it's obvious that they were not a very refined people. Or at least, so say their enemies.
Dutch courage The courage one gets from alcohol. (contributed by Thea Lawton).
Dutch treat And the Welsh thought they had it bad! Yet another slur against the Dutch. Not only are they drunkards (Dutch courage), they're also cheap: if you're offered a "dutch treat", you'll pay your own way.
Scotch tape Possibly apocryphal, but a news item said that "scotch tape" got its name when an irate customer returned some tape with the admonition to "tell your Scotch boss to put more glue on it", using the term Scotch to indicate an unwillingness to spend money.
are you trying to gyp me? The gypsies, of course...probably they're descended from a group that left India in the 1700's, by the way. (Suggested by Ken Revzan)
You're trying to jew me down. As Tom Lehrer says, "The Catholics hate the Protestants, and the Protestants hate the Catholics, and the Hindus hate the Moslems, and everybody hates the Jews." (Suggested by Ken Revzan
You're a Thug A reference to the "Thugs" or "Thugees" of India...but that was a sort of organized crime group, not an ethnic group, so this was sort of like saying "you're a gangster." Doesn't fit the ethnicity requirement, so it doesn't really count, but it's interesting and a good effort. (Suggested by Jim Parinella)
Got more? send them to me at pnprice@lbl.gov.