A typical machinist's scraper (upper in photograph) is very useful for deburring both metal and plastic parts. It is, however, a bit cumbersome for small parts, not to mention uncomfortable to choke up on when doing detailed work.
A better solution is a small triangular file fitted with a suitable handle (scavenged from worn out rubber stamps in my case.)
Attachment 36973
Grind the tip of the file into three sharp edges and you have the best of both deburring worlds, filing and scraping, in one tool that's comfortable to choke.
Attachment 36974
