9mm, I have other caliber guns but haven't shot any of them in a couple of years. With a minimum of 1 match per week up to 3 per week, add in practice and I get plenty of shooting time.
No particular caliber...Mostly my semi's or AR because I have lots of mags preloaded ready to go. (22LR,22MAG,.380,9MM,40S&W,45ACP,.223,5.56) Can't forget my .38's and .357's.
What I take usually depends on how ammo is onhand.
.44 Magnum (I couldn't believe it until I did the math, 1000 rounds in about 6 months)
.22 LR (a little over 1200 rounds a year)
.38 Spl (1000 rounds/year)
.45 ACP (about 500/year, but only because my .45 becomes my .22 for half of the year)
For the last five years 410 bore, 28 gauge and 38 special (and 45 ACP 4th). But I'm hoping that that will change back to 308, 223, and 338 Lapua (and 22LR 4th) this coming year!