Like Charlie said, you COULD live without one, but I sure wouldn't WANT to!

Two tips about a dremel...

There are two different types of cut-off wheels. One is a thin, hard, stone disc, and the other is a fiberglass disc that is impregnated with an abrasive. Throw the stone discs away - they are very brittle and can shatter - flinging fragments in every direction at very high speeds. The fiberglass wheels work better and are MUCH safer!!!

Second tip - get a few of these cutters. They look like a drill, but they cut sideways