Alzrius
The EN World kitten
Honestly, these days I mix 3.0, 3.5, Pathfinder 1E, and even d20 Modern fairly frequently. The systems are so similar that it's easy to smooth over the rough spots, and the sheer multiplicity of third-party stuff out there means that there's something for whatever I could want; having spent over two decades picking up an insane amount of books (in print and PDF), I can make virtually anything now, and it's a lot of fun doing so.
The biggest problem is remembering what I have, and where it is!
The biggest problem is remembering what I have, and where it is!