I have a very short list of people I will trust with one of my bikes.
When I had a VX800, it was such an easy, friendly bike to ride that the list was a bit longer. The GS850, V-Strom, and KLR650 are all way too tall and top-heavy for n00bs.
If someone held a gun to my head and demanded that I loan them a bike, it would probably be the KLR650 -- it's covered in protection, and is thus the most "crashable" by far.
I jokingly offered to let a very short friend take my KLR for a spin once (it's stock height, with beefed-up suspension and a regular height seat). I didn't imagine he would actually take me up on the offer. But he clambered aboard somehow after a running jump, and managed the bike beautifully. At stop lights, he had to slide off the seat to the left to get one toe down, leaving his right leg barely hooked over the seat. When the light turned green, he'd smoothly spring up into the saddle while letting out the clutch. Hilarious to watch, but effective... if you have the skill, you can ride anything.
1983 Suzuki GS850G, Cosmic Blue
2002 Suzuki Vstrom DL1000, Midnight Blue
2005 Kawasaki KLR650 - Turd II, The ReTurdening
"Do not crinkle your food wrappers loudly. Be considerate to others, or I will bite your torso and give you a disease."