It's one of (If not the original) vector tool. What's more, it's ...uh... fantastic! Even if you're not known to use it for drawing, you might wanna get into the effective habit of utilizing it's very easy-to-use Gradient fill tools to add colours. Checkout Popular offender Teruchan to see what I mean.
I think they are all for free (because they were made for linux.....you probably can use them all at an other OS), and I'm not in the mood to go and try them... I don't like to migrate to other programs ... so I don't know if they are any good or not... it's just to let you ppl know that they exist... I've read that some of you work with some programs of the list above