My aunt is not my "ahnt."
A small space is not a "neesh."
One does not conduct "nego-c-ations."
That last affectation is the oldest, I think, at least as far as its use by talking heads. Edwin Newman (who's still alive, as if you care) mocked it way back when in Strictly Speaking, if I remember right. It's bothered lots of people, of course, but it was surprisingly difficult to find examples (I found two) by googling. One, oddly, was in the comments to a post on the (really good) jazzbo blog, Rifftides.
"Niche" pronounced "neesh" is more recent. It's the second pronunciation in the American Heritage Dictionary, so I guess it's not wrong, but it sure sounds wrong, probably because I never heard it pronounced that way until about five years ago. Weird.
"Nego-c-ation" is maybe just a case of plain old snobbery. Makes the word sound more French, so maybe people will think you actually, you know, speak French. Oo-la-freakin'-la.
"Ahnt" is reverse snobbery. To sweepingly generalize (the Drunkablog way!), "ahnt" is how African-Americans often pronounce the word; now, in politically correct solidarity, so do whites (or is it "Whites"?).
Update: The AP stylebook is shockingly sensible on racial designations. Under "African-American" one reads, "The preferred term is black." Under "nationalities and races" it says, "Lowercase black (noun or adjective), white, red, mulatto, etc. See colored."
Update II: As for "colored," in case you were wondering: just don't use it, okay?