Last night I prepared myself to have a merry fight with a set of grab-on handlebar grips. You know, the ones which are famously hard to get off.
After a lot of swearing I got the lower one off. I then began on the upper one when inspiration struck. I took a hypodermic syringe filled with about 1cc of soapy water, and injected it somewhere around the middle of the grip. And Ping! off it came.
(Of course, it helps if you have hypodermics lying around the place. But I hear you can get them from travel places as an emergency medical kit for use in places where sterilisation is an optional extra.)