First off there are way to many "explosions" as you call them to list & it is completely unfair to limit this response to a single event as you call for.
In my humble opinion this is not even remotely possible as an exercise to list just one "Best Guitar Explosion of all Time".
There have been so many great performances over the years, none better than the next just different, unique and/or magical in and of themself.
If we could narrow down the pool of choices by using some variables of sorts it would give us at least a fighting chance at "the Best".
FOR EXAMPLE:
1.) Using a particular "genre" of music
2.) Picking a specific period in time
(i.e. 60's, 70's, 80's...etc)
3.) Having some other sort of other classification or label that would narrow down the field
(i.e. artist vs. band, dead vs. alive, live vs. studio
etc)
As a guitar player & connoisseur of all types of music my experiences go back now almost 40 years so I would like to think I have a little of a track record and personal experiences to pull from.
OK, now that I have that off my chest and was able to throw in my 2 cents I will give at least my Sunday 05.13.07 Explosion.
This is a selection that has always been up there for me personally as one of those "magical moments" that over the years seems to be often imitated but never duplicated.
This from the current "hardest working guitarist in the biz":
Mr. Warren Haynes of Gov't Mule
We will be choosing the following event (Warren has had countless nights that have brought grown men to tears so the explosion selection I am going after could be anyone of many he has thrown down with);
song: TEMPORARY SAINT > THORAZINE SHUFFLE
5th track of the evening ~ Set #1 (depending on how your copies tracking is)
where: 4:35 +/- of Temporary Saint is where the "Explosion" as you so eloquently put it is beginning to erupt, this then continues on for several more minutes
)
date: 08.30.1997
venue: The Fillmore
city / state: San Francisco, California