Pencil and watercolors ^^
And nope, if someone gets a request for free, they shouldn't be taking it for granted or act like you're some sort of art machine.
You're drawing the pic for them because you -want- to. You don't owe them anything, so you're free to work at your own pace, or to just tell them you don't want to draw for them, if you change your mind.
And here's something I've drawn, for good measure xP