Repair gouges in a particle board desk?
Depending on how closely you're going to try to match the original finish (or if close enough is close enough) you could use wood filler.  This product is basically saw dust and glue.  Most of them are stainable, so you could fuss with it to match your desk's finish.

This is an example, I am not affiliated in any way with any company in the link, just the first thing on google.