Currently, I swear by Ernie Ball Super Slinky's: 9-46. There was a period when I was into Testament and tuning down to C# or something like that, and for that I used the heavier Ernie Ball sets. Now, following the path of Vai, I moved back to 9-46. They're easier on the old fangers when doing crazy stuff. Either way, Ernie Ball rules. They last really long.