The current post on Language Log about uncountable nouns becoming countable reminded me, obliquely, of the usage “a swear”.
I told a kid off in class for saying “For God’s sake” or some such, and he complained that it “isn’t a swear”. I hadn’t heard “swear” as a noun before.
Hard to google for examples, but I did find a cartoon with “a swear” in the title (and it includes a variant of “could care less“):
Checking on dictionary.com, “swear” is in AHD4 as a noun, but not the other dictionaries.