Hey guys was just wondering what was the best air gun caliber y'all prefer for deer?

NONE Troll! Deer deserve more respect than that and you deserve NO RESPECT!

I can not agree more, but lets be fair the guy asked an honest question. Can I shoot a buffalo with an airgun? Sure I can. Do I personally want to? No not really, but I can.

Back to the question. I would not shoot any game animal with a caliber smaller than .22 (5.5 mm & 5.6 mm)
If you want to you can go bigger, I would recommend shooting a .45 and it has to be PCP.

Just make sure you are dead on with your airgun before attempting to take a game animal. Be comfortable with the gun and its capabilities.

.25 (6.35) or .30 (7.62) should be best for deer hunting but its depends on pellets grain as well.

Same question i am looking.