You want something that people will use... champagne glasses tend to end up on display in the breakfront, but highballs, pint glasses, and the like get used. I still use the pint glasses from one of my semiformals as water glasses... but the champagne glasses from senior formal sit in the breakfront and gather dust.
Or you can do keychains. My local did a date party once called "The Heart of a Treasure" - sisters and their dates got keys on a keychain, and you had to find the person whose key matched yours - he was your date. The keychains were the favors.
A great-aunt and -uncle of mine had a 50th anniversary celebration when I was little - their favors were decks of playing cards. Don't know where they got them done, but it's an original idea.