Only one (the last one) is from a children's book.
- Big Brother from 1984 by George Orwell
- Hannibal Lecter from the novels by Thomas Harris
- Pennywise the clown from It by Stephen King
- Nurse Ratched from One Flew Over a Cuckoo’s Nest by Ken Kesey
- Count Dracula from Bram Stoker’s novel
- Annie Wilkes from Misery by Stephen King
- The demon from The Exorcist by William Peter Blatty
- Patrick Bateman from American Psycho by Bret Easton Ellis
- Bill Sykes from Oliver Twist by Charles Dickens
- Voldemort from the Harry Potter books by J.K. Rowling
Incidentally, if you don't already know about it, AbeBooks is a great online resource for finding used books.