Terry Pratchett

Rincewind the shoemaker ? Rincewind the beggar ? Rincewind the thief ? Just about everything apart from Rincewind the corpse demanded training or aptitudes that he didn't have.

He was no good at anything else. Wizardry was the only refuge. Well, actually he was no good at wizardry either, but at least he was definitively no good at it. He'd always felt he had a right to exist as a wizard in the same way you couldn't do proper maths without the number 0, which wasn't a number at all but, if it went away, would leave a lot of large numbers looking bloody stupid.