A hefeweizen. Had a near disaster where after purging the keg of CO2 I forgot to shut off the valve and drained my tank while racking the beer, but I was able to get it re-filled quickly and it's now hooked up and purring away. Then there was that whole hissing sound after I dropped the PSI a bit, but that stopped so it just must have been the pressure regulating itself out.
That was nerve-wracking. Here's hoping that I will have carbonated beer and not crap in my keg after a few days!