Hide games we haven't played
There are some free-to-play games in my list that I've never (that I recall) played (AdVenture Capitalist, Double Action: Boogaloo). I think hey shouldn't show up in my list until I play them. Team Fortress 2, on the other hand, I have played, so it should be in the list, but it isn't. :-)
In general, I could see being able to exclude games from the list could be useful, too.
Definitely planned, should go along with optionally hiding games in your Wishlist from “My Games” view and My Games stats.