This is a hard question. Perhaps because I am so easily impressed.
Some ...
Terje Rypdal's Odyssey in about 1976 in Oslo.
Randy Weston - Keystone Korner, San Francisco
Jack DeJohnette's Special Edition with Chico Freeman and Arthur Blytthe - free concert in Beacon Hill Park, Victoria, BC.
Peter Gabriel, the US Tour - best sound, best performance, best combination of stage-craft and music, I have ever heard.
Richard Thompson with Clive Gregson and Christine Collister - small club, very small - my ears are still bleeding - every pint Thompson finished caused him to reach for the volume knob on his Fender Twin.
Jim Hall ... every time.
Richard Thompson and Danny Thompson Tour.
Bert Jansch - every time.
Leonard Cohen - final tour
Van Morrison - tour with Bob Dylan and Joni Mitchell
Joni Mitchell tour with Jaco Pastorius and the Breckers etc.
Shelia Jordan - every time.