Here is an article on Yahoo Finance that lists 21 items never to buy new. I pretty much agree with all of them, except I would add underwear to the list. 
I especially agree with timeshares. My folks bought some timeshares on the secondary markets years ago for next to nothing. They got tired of paying the maintenance fees so they “gifted” them to my sister and me. We are at a point where we wonder if we are just better off getting rid of the timeshare or keeping it. They are nicer places than a hotel, but I don’t travel as much with my own business. Or, I am shuffling back and forth between Florida and Maryland to visit clients. Anyway, we rented a week out last year for friends of ours, and I specifically told them not to get caught up in the timeshare tours. They received a call each day offering free Disney tickets to take a tour. They succumbed to the tour for the tickets, but ended up buying a place from the salesman. I almost punched my friends in the face when they told me. Instead, I held back and merely asked if they were idiots. Probably not much subtler, I know. I then proceeded to show them how many timeshares are for sale on ebay. I probably shouldn’t have done that either as you could see the buyer’s remorse. So if you want a timeshare, especially after the dog and pony show for free ticket trick the salesmen offer, then hit ebay or craigslist. They are deeded properties so you get no benefit for paying full price, except the satisfaction of helping the salesperson pay for their sportscar.
Cars are another no brainer. Sure, you don’t get the new car smell, but you can buy that smell as an air freshner.
Anyway, a good list of items. What else do you think should be added to the list?