Stripping off the old tile which was under the carpet. I used an air chisel for that, and also (for some easier parts where the tile wasn't sticking too well anymore) a scraper made by bolting a brick chisel into the end of a piece of fence pipe. Drilling the brick chisel was hard, because it's cast iron. But that was a couple years ago, when we needed something like that for the floor in another room. It has some heft, thus some momentum when it's moving, and plows through stuff on the floor pretty well. But you feel it in your arms after a while. I'd have big arms if I did that every day.