I may forget a few I've built for customers, but I personally own or have owned 22LR, 17WSM, 17 rem, 17Mach IV(disaster), 20 Prac, 204R, 223rem, 223wylde, 5.56x45, 223AI, 6x45, 243wssm, 25 wssm, 6.5 Grendel, 264 LBC, 6.8SPC, 277 wolverine, 7 valk, 300blk, x39, 450 Bush, 458Soc, 50beo.
Personally, the 223 wylde and 5.56 make the most sense for a general purpose "joyful" rifle. The mid-bores like the 25-45, 6x45, 6-6.8, 243lbc, 6.8spc, 6.5 grendel/264 LBC really are the most versatile. I love shooting the 458 soc out of the AR, just as I love the 458win mag in a bolt repeater and the 45-70 in a levergun, but the heavy weights really do lack in versatility - too much recoil for small game, and not really any better performance on mid-sized game like whitetails and hogs than the 6.8/6.5's, so unless you're going after short range bison, the big bore AR's are just a novelty. The x39 and 300black are cartridges which don't interest me any more. The trajectory is weak, so they fall short on deer/hogs compared to the 6.8/6.5's, but they don't yet hit as hard as the 450/458/50... Kinda like a full size truck with a 6 cylinder, they'll get you to work well enough, but when you really need to work, you'll find a weakness. The WSSM's were an absolute joy, AR-10/LR-308 performance out of an AR-15, but it's also hard to call the Dtech (oly) uppers true AR-15's, since so little about them is transferable. If the brass were 1) more available, and 2) much, much better, I'd still be shooting the 243wssm, but until then, I'm content to run 243win DPMS GII and 6.5creed LR-308 customs instead.