The metal slinky-type belts. Ladies, many of us over-30s made this fashion mistake once in our youth. Please learn from us and don't do it again.
Overly cutesy sweatshirts (the cartoon kitties, things like that) worn in public. Especially on (ahem) zaftig women. Please, please, have some dignity. Shop in the men's section if you must.
Burberry matching plaid bag and shoes. I used to love that pattern, but it is sooooooo played around here.
***edited to add in response to Meliss's post, I always get amused when people condemn "ugly 80's clothes" when what they are wearing is a redo of...ugly 70's clothes.
FYI, most people did not go to school/work looking like Cyndi Lauper...the prevalent 80's style was more preppie than anything else.