Well-rounded "stock" characters

In my group, for all the games we run, whoever runs the game has been asked to put together 2 or 3 well-rounded "stock" characters in case someone really doesn't understand how the system is supposed to work and completely misappropriates his points, or in case a non-regular visitor comes over and wants to sit in.

The general idea behind the character is that it's not at all specialized, but good enough that the character can adapt moderately to most situations. The key here is that the character is less about developing as a character and more about allowing the player to jump in and learn the mechanics.

Whew.

Having said all that, what suggestions do you have for developing "well-rounded" characters? I'm going to generate 2 or 3, so we'll have a doctor or an engineer if need be. (Knowing my group, I won't need to pre-generate a security officer :D ) What skills/specializations do you find frequently recurring or particularly useful?

My own take on this is that it's better to have lots of 1(2) and 2(3) than 3(4) or better, but I'd like a second (and third, and fourth...) opinion.

Thanks!