I have loaned special guests the same rifle that I usually use, a Sako AV classic custom .35 Whelen with Zeiss 3-9 scope. Or a Sako L61R full stock carbine 30-06 with Karl Kaps 6x. They are both top quality and work very effectively.

The emergency loaner that we keep in camp is an old ( almost 100 yrs old) #4 SMLE Lee enfield .303 british. Original battle sights and the full stock cut down to save weight. So far it's been carried a couple times but not shot.
It is the same configuration as a rifle that I killed my first deer with. Not glamorous, not precise, but good enough to keep "just in case"