It's hard to go wrong with a .30-06. The best gun to use on hogs is the one that you can place your shots with. Hogs are tough animals, and a wounded hog can run a long way. I had this happen last week when my first shot didn't go where I wanted it to.[:@] Could've been the brush, could've been the high winds, could've been the poor light, could've been me shivering, could've just been piss poor shooting on my part. Took awhile to find the hog, but thank God we did. I used a Remington 700 BDL with 165 grain handloads.
Under ideal conditions, even a small caliber bullet behind the ear will work, but I have yet to experience ideal conditions, so I leave my .243 at home when I hog hunt and take my ought six.
Next time, though, I'm going to try my 8x57 Remington Classic, and after that I'm gonna try my CZ 550 6.5x55 with 140 grain bullets. Both rifles are very accurate and have the power and penetration to do the job (assuming I do my part.)
Whichever caliber you choose, just make sure you can hit with it, and you'll do fine.