You can use a regular hardware store hole cutter on soft material like wood, but it is difficult to cut really accurate large holes through hard materials like steel or tricky thin materials like sheet metal. For that you’ll need a Rotabroach Hole Cutter, which can make precise circular holes in plate steel and other metals. It can do this because it has machined teeth like a skill saw blade, rather than the stamped metal of a normal hole saw. It also only requires a dimple in the center instead of a drilled hole which can make it trickier to get started, but you get the center piece out whole which is sometimes helpful.
A cool tool is anything useful that is superior to comparable items. If you think this tool is inferior suggest a better one. You are welcome to insult a tool, but comments containing insults to individual people will be deleted. Corrections of fact are always welcomed, if stated politely. Recommendations of better tools are dearly wanted and may be elevated to the front page.