Scheme, since it is so simple. Very easy to learn. No syntax, no comma, no semi-colon. I would have been delighted to learn scheme as my first language rather than c.
This. Scheme was the first language I was ever taught rather than clumsily working out badly on my own, and it was a joy.
If you've not yet had your mind (irreparably ?) damaged by prolonged exposure to imperative languages then programming in Scheme is a wonderful experience in which everything is so simple, clear, and intuitive that it feels like everything is not only possible, but easy.
The only other language I've ever actually enjoyed using is Lua, which would also not be a bad choice.
