I have an branding iron that is heated by torch. Like it, but it can be to big of a signature for some things. Like Flarud stated, it can be hit and miss, so what I did is when I had it heated just right, I branded a piece of veneer several times. Then I cut the veneer when I need a signature and glue it in place. It even looks nice, especially it the back of the project is painted. When I don't have enough room for the branding iron signature I use a sharpie, or it have a signature I can print off the computer, onto decal paper. Ply it where I want it and spray finish over it.
Then I have a set of Steve Good's medallions that I really like. I haven't had a reason to use them yet, but I will.
Then there are lots of time I forget all about a signature.......