While most of us have a favorite defensive firearm, we just might not have that gun with us when trouble rears its angry head. It might malfunction, it might run empty or it might get hit by a bullet. It won't do much good to holler “King's X” in the middle of a gunfight. You'd better find something else to fight with. And you'd better know how to run the closest gun that you can get your hands on.
Close friends, spouses and couples, especially, should know how to make each others guns run. You may prefer a revolver, she may prefer a Glock 17. Fine, keep your favorite, but know how to run the other. That way, you are good to go with whichever firearm is closest when trouble starts.
There are quite a number of shooting ranges across the country that will rent various guns to customers of the range. It can be not only informative, but fun, to just spend a day at this sort of range shooting various kinds of guns that you don't have much previous experience with. Who knows, you might just mess around and find another defensive firearm that really suits you better than what you've been relying on.
That would also be a good project for your local gun club. Bring a variety of members' guns to the line and let your fellow members get some experience shooting and functioning the various action designs. Running an autoloading shotgun can be quite different from that pump you're more familiar with. The AK-47 and the Steyr Aug are both popular fighting carbines, but they run a bit differently. Even old model and new model single-action revolvers load a bit differently and have different safety considerations.
They say that knowledge is power. And expanding your firearms knowledge can also be fun. Either way, learning to run various kinds of defensive firearms just might save your life.