Another vote for Guitar Johnny on Birds of Fire.
AlChuck, much as I like Beck, I thought His Goodbye Pork Pie Hat solo was way cheesy - basically just proved that not only couldn't he solo over changes, but he wasn't even gonna try.
Other faves:
Kath - 25 or 6 to 4 (Chicago)
Trower - Day of the Eagle
SRV - Let's Dance (Bowie)
Beck - New Ways / Train Train
Carlton - Spiral (Crusaders)
Becker - My Old School (Steely Dan)
Baxter - Little Darlin' (Doobies)
Allman - One Way Out
and...
...the endless solo in Boz Scaggs' "Loan Me A Dime", Boz and Duane trading licks (was there a 3rd guy?), though I think I was digging the arrangement more than the solos.
There's also an Eric Gale solo from some CTI session that just knocks me out, and one of Jimi's solos from Band of Gypsys, but I forget which tune.