For ACTUAL jamming, i.e., rambling improv:
Who Knows by Hendrix, I can go miles from shore with that one, and it's always a chance to have some fun with my octave, delay, and phaser pedals.
Likewise In-A-Gadda-Da-Vida with effects, especially doubling the organ using an octane pedal for heavy guitar lines. I like the crudeness of the Boss OC-3 with crunk drive for this, it does its own thing without my help when I stop playing, like a living thing.

I try to imagine what was going through the mind of Mr. Dolarhyde whilst playing......but not for too long......
Interstellar Overdrive - The Floyd
Barracuda - Heart (and of course Mr. Fisher)
S.A.T.O. and Believer - Guess who.....
The Green Manalishi - Old Skool Peter Green style hybrid with some Priestly moments
Dissident Aggressor - Old Skool Priestly style with some Slayer moments