Steel Panel Nibbler/Other Rectangular Hole Cutter?

Do any of you have suggestions for a tool for cutting rectangular holes in panels such as for switches and the like?

I have heard of a "nibbler" type tool but never used one except the ridiculous pliers type ones as seen on TV years ago and they were ridiculous.

I am thinking sheet metal but also occasionally something substantial maybe up to 1/16" and thicker if aluminum.

Ideas?

Steel Panel Nibbler/Other Rectangular Hole Cutter?