this depends on several factors,.. What sort of material is it made from? how small/large is the piece being cut? Are there any weird angles? is anything else "in the way" that shouldn't be cut? If it's plastic/fimo/green stuff then a hobby saw/coping saw/or even a rasp/file if the piece is thin enough. I'd just say to maybe try to steer clear of any "high speed" tools like dremels, as they can chip/burn the plastics. On metals however, a dremel with a thin cutting wheel can be your best friend ever. A thin bladed coping saw can be useful for weird angles or tight spaces.