So like most developers, I pretend to also do graphics somewhat competently. I've used Photoshop, spent a lot of time with the latest Corel Suite. Just recently, Microsoft released their foray into the space with a beta product code-named Acrylic. It's actually the result of a purchase of "Expression" and rebranded, and from my intial look, seems fairly useful as a vector tool.
Most developers keep a graphics tool (besides Paint) in their toolbox for quick and dirty items, and since it's free during beta, Acrylic's not a bad choice.