For his son's eighth birthday, Brad Guigar (of Webcomics.com and Evil, Inc.) made his son a "Lego minifig customization kit". It's stuffed with blank and generic minifig parts, primer, paint, small brushes, and a solderer's clamp for precision detail work, all organized in a convenient case.

It's a brilliant gift, and I'm a little envious of his creativity in giving it.

Full disclosure: I'm totally stealing this idea (in a few years, when my daughter is a little bit older.)