There are a lot of ps+ games I downloaded, started, deleted. To narrow it down to games I actually bought full price at release, there was Rockstar table tennis game on the 360, recommended by a friend, went back to the store the next day.
Xenoblade Chronicles X I only played the tutorial, was boring and didn't like the style at all, returned it later.
Least played on Steam: Primordia at 1 minute.
Ofcourse there are plenty games in my library I haven't even started.