What's a good tool to remove old caulking with?

A painter’s chisel.

A putty knife and razor blade works for me.

Stanley blade to break the seal and then the back of a chisel.

I use a five-in-one tool for scraping caulk and a billion other things. One of the most useful tools I use.

As an ex tile guy. I have always just used a razor blade and a knife….... Has alway worked for me

My husband. (j/k) Seriously though, my husband caulks buildings for a living, and the thing he uses is a five in one tool. (I would think tapping it in with a mallet would help too depending on the hardness of the surface that the caulking is on, and how tough the adhesion seal was.)

I have done various home improvement projects, but in no way am I an expert, but the razor knife does a good job, but I had a tool once that had 90 degree bend with approximately a 1/8 tip, in a triangular shape.
The razor knife loosen’s the majority, but this little scraper, would clean the area. I want to even say I might still have it.