In this category are all the bikes I have borrowed, the only bike I have ridden any distance is Hesh's R80 which I ferried back to California from Utah after the Battlestar crashing contest.
Suzuki 250 Hustler - probably rode this less than a mile but it was my first ride.
Honda CBX1000 - the amazingly smooth inline 6.
BMW R80 (ST?) - Hesh's famous bike, already had over 100,000 miles on it I think.
BMW R80 - A very similar bike belonging to Phil who was busy "seeing what the Hurricane could do" at the time.
BMW R100S - Belongs to Bob who I went to Alaska with.
Honda XL650R (or XR650L) - Honda's almost street legal DP bike with a kit to get it registered. Rode this in Death Valley swapping with Doug who had a passenger whose BMW had let her down and the KLR was much better suited to pillions.
BMW R1150RS - took a test ride at Brecht BMW in Escondido, nice enough bike but lacking a purpose for me.
BMW R1150RT - again at Brecht - I bought mine the same day.
BMW K100 - loaner from Brecht - it vibrates and the seat is hard as a rock!
BMW F650CSL - hideous thing, loaner from Brattin while my RT was being worked on.
BMW R1150RT - when my RT transmission went out I borrowed this one to cover the 850 miles home
Harley Davidson Road Glide - this bike surprised me, I liked it for the 130 miles of Texas backroads we covered, much smoother than I expected though horrible at idle.
BMW K12RS - rode this sporty BMW from Torrey to Los Angeles to return it to its injured owner, very nice bike.
There are others but I can't bring them to mind right now.