Stealing candy from little children (well, that's not really bad, it's better for their teeth).
Helping old ladies crossing a busy street, abandoning them halfway.
Giving bad advice on Perlmonks.
Illegally copying and distributing Microsoft software, and modified GNU software in binary only format.
Burning live ants with a magnifying glass.
Defacing web sites.
Collecting email addresses, selling them to spammers.
Borrowing cars from people I don't know.
Installing hidden cameras in dressing rooms.
Telling mothers their babies are the ugliests creatures I've ever seen.
Snooping wireless networks for passwords, credit cards and porn.
Letting my modem dial random numbers during the night.
Voting republican.
Making lewd comments to women.
Asking strangers why the missed the last weekly dark room session - was it because of a disease? (In a loud voice so others can hear it).
Call the cops, say that my neighbours speak Arabic, take flying lessons and carry maps of the White house.
Pick flowers from gardens.
Putting fireworks in the mailbox.
Smoke in restaurants. Complain the menu has a lot of meat dishes - farm animals are not well cared for. Insult other patrons for eating meat. Order a steak anyway, because humans are nearly as smart as cows.
Parking in handicap areas.
Cutting in lines.
Farting and burping in movie theaters. Scedule to be called during the movie - and then answering the phone in a loud voice.
Gossiping.
Cheating on my tax forms.
Ordering pizza with weird toppings. Send it to someone elses address.
Paying with a $10 bill. When getting chance, claiming I paid with a twenty.
Fishing and hunting without a license.
Dialling 911 from unguarded phones (in shops, restaurants, or the cell phones co-workers leave on their desk when stepping away) reporting fires, accidents or crime.
Comment on Re: [OT] General bad habits and characteristics (non programming).
I hope you have one more bad habit that you didn't mentioned - too much irony. Because if you don't, you're in serious trouble, and need proper help :)