I'd like to find a powder I can use in both 5.56mm and 7.52mm blasting ammo, with an added bonus of .30-06 M1 Garand loads. Right now I use 3 different powders (H335, IMR3031, and IMR4895, respectively...) and I've not found a whole lot of interchangeability between them. H335 works in both the 7.62mm and .30-06, but it's not the best choice by far. Similarly, not fond of trying to fit all those little Lincoln Log IMR powders into a 5.56mm case on a progressive. Yes, IMR4895 works with both the .30's, but my short-barreled M1a works better with IMR3031. The answer to all of this might very well be TAC... and I've been trying to get my hands on a can of it for about a year.
As far as pistol powders... about a year and a half ago I set out on a similar quest as my rifle powder... to find a powder that works well in both the 9mm and .45ACP out of short-barreled pistols. To say I was underwhelmed by the newer powders would be an understatement. Nothing worked as well as tried and true Unique. I did, finally, come up with an alternate... and that's W244, which if you load it within it's narrow parameters, behaved pretty well. So, what's old is new, again...