1. Late '70s/early '80s: The cover came straight out of Animal Hell, with an illustration of an oversized rat standing on its hind legs, holding the decapitated head of a cat in one hand and gouging its eye out with a bone in the other. Some other vague recollection of the cover includes a pile of bones. I think there also was a little more text on the cover than most books, which leads me to believe it was an anthology of some sort; however I am not positive about this. I remember absolutely nothing about the author(s), title, or back cover. Found! It’s Dr. Rat, 1977 Bantam edition.
2. Unusual horror anthology that came out in the early '60s. It was paperbound, rather thin, and oversize, roughly 2X the dimensions of a paperback. The cover was dark blacks and purples with creepy drawings overlaid (I believe, going from a half century old memory!), and each of the short, 1- to 3-page stories had an illustration with it. Each story had an EC-like twist ending.
3. '90s or early '00s. It was a book of ghost stories, possibly British or Irish. I think there was a story about a banshee, and another about a ghost carrying a coffin and then appearing in an elevator as a warning, but the story I really remember is one where this girl, every birthday, tells her family a man (possibly named Billy, or William) will come for her. Year after year, he doesn't show - until her 18th(?) birthday, when the candles blow out and he appears on a horse and takes her away.