I bought myself two lovely craft punches (on Amazon) - two different sizes - 1 inch (2.5cm) and 2.5 inches (6.25cm). I had held off, as I don't want to be buying tons of art supplies that I don't use. But these will get plenty of use!
They are the ideal tool to use up bits of gelli prints that didn't quite work out. I can see myself using them for greeting cards of course, but I've already started using them for journals (see Documented Life Project label).
They work best with card paper, but will also do the job with lighter paper, though I found you may have to pull and cut a bit by hand with newsprint - that's just a little bit too light.