I posted a thread on the Steam Forums asking what people would like in a future Inventory game or expansion pack/dlc. Most were suggestions for new characters. Seeing as it it's Valve's own forums there is obviously a bias towards Valve characters, but the top two characters were actually Duke Nukem and Guybrush Threepwood. Here's a link to the thread.
and here's a list of the top votes (some people got the same number of votes):
1. Guybrush Threepwood
2. Duke Nukem
8. Ben "Yhatzee" Crowshaw
11. Gabe Newell
Thought I might as well link it over here and see what the Telltale fans thought of the Valve fans' choices. (My votes, by the way, were Guybrush Threepwood, Nick (L4D), Abe (Oddworld) & Duke Nukem)