The original poster was right, people do not really know what a cult movie is. A cult movie is one which most people do not know or think not much of it, but which some people like very much indeed.
For example, that terrific film 'The Sweet Smell of Success' is not really a cult movie because it was universally recognised as an excellent film - nor is 'Kiss me Deadly' for the same reason.
However, how about 'Harold and Maude'? I think it is terrific, original, funny and affecting. Also, I think that 'Assault on Precinct 13' qualifies, because a large number of people don't like it. Ignore the remake which is pants.
'Vanishing Point' was quite popular in GB (because we liked Barry Newman as Petrocelli in the TV series) but still qualifies becaue it is also much hated. The remake is the most pathetically bad effort to 'Christianise' it and turns it into sentimental tosh.
Finally, have a look at 'Johnny Guitar'. If you don't like that, give up and stick to mainstream stuff.