What kind of drill and bit works best?

It is best on a drill if it is a 18 or 20 Volt. Ice is very hard and lower voltage drills can work, but I have seen a few struggle and burn up with the effort.

The kind of drill bit that we use is called a Spade Bit. I usually use a 1" bit for small globes and and 1.5" bit for large globes. With an extender on them, it makes it easy to drill all the way through a forgotten globe that has frozen solid so one can run hot water through it to create a cavity that is big enough for a candle.