Fortunately I don't have many photographer friends, and out of the ones I do have they either shoot with a Nikon or are a bit odd & will only shoot with their 70-200 L because "it's the best lens so why use anything else"
I'm a bit possessive of my kit too so I'm not really sure, I suppose it depends who it is I'd probably loan the 70-200, 35mm & 75-300 & a flash but not my camera, 50mm or 100mm although I'm more than happy to share my kit when I'm there.