A big two jaw gear puller does the job, and people have using ujoint/balljoint presses also. Both are super scary compared to the right tool.
That being said, I use a 7ton 2jaw gear puller from Sears. I use the longest breaker bar I have, and I tie off the gear puller to the frame so if it comes off, it doesn't go too far. Maybe wear a helmet if you have one!