Required guns is very subjective to personal taste and geographic location. Coming from a small town, rural environment I can tell you there are a good many people, even serious outdoor orientated people, that get by just fine with nothing more than a 12 or 20. Heck, there is guns listed here in top 5's that wouldn't make my top 10. Heck, some wouldn't make my top 20. In most if not all cases these lists are much more geared towards wants and perceived needs than actual needs. That's cool, to each their own.
1) 12ga pump with multiple barrels. Prefer an 18" smoothbore slug barrel w/ rifle sights and a 22" choke tube barrel. Longer barrel would be nice (and yes I do have one hiding in the dark recesses of the safe) if there was still any upland game and I don't do ducks/geese. But with 2 or 3 barrels that just ain't much needs done that can't be done.
2) .22 rifle. Preference towards semi and specifically the Ruger 10/22 with some trigger work thrown in. Not much this will do that a shotgun can't but it's quieter, handier, lighter ammo, etc.
3) Centerfire Rifle. This is really just a want around here. Coyotes, vermin, etc. Again nothing that can't be effectively killed with a shotgun but it can't be argued that it's range adds a pleasant benefit. My choice, .243.
4) A Kit gun. In all reality I have 4. Bounce back and forth between a Bersa T22, a 4.5" Ruger 22/45, a .32H&R Single Six and a 3" S&W M36 in .38sp. In reality they all work for the needs of a Kit gun but I'm leaning towards the M36. It's my newest, the one I've looked hardest for AND it's more "conventional" for the next item than the others. Pick one.
5) CC gun. In reality you are far from unarmed with any of the kit guns at your side but if you're a stickler for proper cartridges/platform than you may want to add this to your collection. I won't.
If you can't get by with this list you're probably doing something wrong. (LEO's being an exception, add a full size handgun).