A revolver, preferably one chambered in 357 magnum, which can be used with lighter .38 shells for novice shooters. Never jams, no manipulation required other than to understand the basics of point and shoot. The Ruger SP101 is an unbreakable, reliable beast of a handgun that anyone can get up and running with 10 minutes training - and it’s small. Just one example, there are others out there. But unless your friend is going to train, give them something easy to use that is most certainly capable of protecting them from anything that comes their way.