There is no way I claim this is the best, but I tend to grab/work with whatever is handy. I have used, numerous times, a pipe wrench to gently twist and break loose stuck grips. :shock:
Crescent wrench sized down to the exact size of your handlebar. Place it behind your grip and hit the wrench with a rubber mallet. Pops right off
Make sure you use a rubber mallet and not the claw hammer in your box. Otherwise that expensive lifetime warrantied wrench gets too dinged up and the warranty doesn't cover misuse. How do I know this? Well......I now have a crescent wrench that's sole purpose in life is to pop off grips because one wrongly placed hammer blow made sure it was never again to be an "adjustable wrench"
I use "Vonpotter's" method. 7/8 open end wrench or crescent depending on size of handlebars. Has never failed me yet & normally doesn't harm the grips.