Wicked cheap diamond hole saws. I've used them many a time and they're more than capable of performing the rudimentary task of drilling a glass aquarium with a hand drill.
They're cheap, they ship/arrive quickly, and it's always good to have a few on hand.
Or, if you want, you can swing by my place in Worcester and I'll drill it for you. I don't charge anything, however; feel free to bring a six pack or micro brew. I've never shattered a tank to date, but there's no guarantees