I would be totally hosed without a Dremel tool.
The negative battery contact on my truck was in pretty bad shape due to corrosion buildup, but the cables were still intact and very heavy-duty. So I used the Dremel to cut what was left of the contact away, then cut through the old bolt because it was too corroded to unscrew. Then I drilled out the hole where the old bolt had attached the contact to the cables, widened it and got rid of all the leftover corroded metal shards, then put on a sander and ground the whole thing until all the corrosion was gone and I had a bright, shiny, smooth contact. Then I just bolted it onto the new heavy-duty contact I got from NAPA yesterday and now the truck starts with no problem.
But if I didn't have a Dremel tool, I don't what I would have done. My only complaint is that it's one of those single-speed (30,000 rpm) models, but then it was a gift, so I'm not complaining. But I would like to get a variable-speed model.