I personally love redirecting users the hamster dance or hitting them with a Rick Roll. To keep it short, your imagination along with a developer is your limit. So do me a favor and piss off spammers by rebelling. Send them to annoying sites providing you with a satisfying feeling of cleverness. Alight, I'm done venting.
If you decide to redirect spammers from your web form, I want to hear about. Comment in what irritated you and what you did as a corrective measure.