One of my favourite introductory one shots was giving everyone an empty character sheet (excluding equipment) and letting them know their characters had amnesia. I'd written up sheets for everyone in advance, and only told them an ability score, or skill score when they actually tried to do it. Might not work for everyone, but it got them to try lots of different things!

In the end everyone had a decent idea of what their characters could do and we took those characters into a more regular game!

Edit: I should add that the actual adventure was rather generic, defend the Abbey against the bandits, with a few simple skill checks for stuff like climbing, investigation, knowledge etc.