it was a serious answer you know, the best results i have had stripping poly finished guitars is with various sanders and sandpaper, and a fair amount of elbow grease. its a bitch around the edges and cutaways and takes longer than you would expect to get right... but it works and it wont harm the wood underneath as long as you make sure to sand evenly
now the real question, why are you stripping it?
If its to redo it a different colour then you will be better off just sanding the shiny surface off and finishing over the top. its poly anyway so adding more shouldnt harm the tone and it saves you a lot of hassle i the long run
if its to have a natural finish, do you know what the wood looks like underneath and whether it will look good natural
here is something from the reranch website to consider
Should you ever have the unfortunate job of stripping a polyurethane finish, I have found only one chemical stripper which will remove poly; AirCraft Remover by Kleen Strip. It can be found at most automotive paint supply stores. Be aware that should you decide to use A/R, it is deadly to plastic bindings. Protect the bindings and if possible strip with A/R only up to near the binding area and use lacquer thinner or sanding to remove the finish adjacent to the bindings. One trick; on stubborn finishes, cover the area being stripped with a plastic garbage bag to prevent the stripper from evaporating. This will give the stripper a longer working time. Test the bag first to be sure that it is not attacked by the stripper although most bags do not seem to be affected.
they also talk about using heat guns to shift poly but i havnt tried that