It's not a case of "what am I playing" so much as "what am I making". A recent play of UT3 got me back into UDK (Unreal Development Kit) which allows me to make mods for Unreal Engine 3-powered games that I own - Unreal Tournament 3, Borderlands 1+2, a couple others.
A simple process for a professional video game development tool (and it's free, too), yet still very tedious and rewarding for the patient.
So far, I'm making UT3 remakes of my favorite Unreal and Unreal Tournament maps - Morpheus, Sesmar, Barricade, etc.
Barricade is my main one because there's so many different ways I could remake it and just the thought of having so much freedom to tweak it to my tastes is just so delectable.
I wonder if I'll ever finish though.