What I think and what I own are two different things.
Reccomended essentials for general shooting and sporting.
1. A rimfire rifle- all around usefulness, small game, target shooting, plinking, time filler when varmint shooting or long range days, a trainer for friends and family.
2. A rimfire pistol or revolver- same reasons as above
3. A good handgun in a common calibur - A primary sidearm that is not behond your personal limits for practice/training, range shooting, personal defense.
4. A 12ga. shotgun- The older I get, the more I end up getting invited to bird hunting trips, sporting clay shoots, trap shoots and hand thrown clay shoots. This is an excellent source for fun, it's hard to get excited over a non-tactical shotgun but money well spent. granted there is no such thing as an all purpose shotgun but 12ga. is more general and can be used in many more types of shooting and hunting.
5. A "go too" rifle- Again, there's no such thing as an all purpose rifle but you can get fairly close. A good centerfire rifle can be used for hunting, range shooting, developing fundimental skills, home and personal protection, and even be employed in tactical scenerios.
6. A hunting rifle-I have a .308 bolt gun but it's really heavy for hunting. I use it for hunting sometimes but it limits me quite a bit. Even if your not an avid hunter a high-power rifle (especially in a bolt or breach loader) is much more enjoyable to shoot than most guns due to emphasis on single shot placement, range calculations, wind calls, mirage, load develpoment. It's an exploration on the technical side of shooting.
7 (if you have a CCW) A good carry gun - Carry guns are a very delicate balance between stopping power, capacity and concealability. Finding one that works for you may take more time than you think.
Many guns are very specific for use. Take for example the PS-90. This is designed as a PDW or a CQB gun. It's not nearly as versitile as say an AR-15 which is why it didn't make my essentials list.
Shotguns perfect examples of how specific guns can be. pheasant hunters and duck hunters use very different guns (don't have to but it's much better if you do) Same with Turkey. Of the difference between trap and sporting clays or tactical They are all very different machines.