My favorites in order:
1. .303 British in 180gr - It's big and slow, and it flat out drops deer
2. .308 in 180gr - It's just a great all a round cartridge (and it's put two slick heads in the freezer this year)
3. 7mm Mauser in 162gr - Another great all a round cartirdge. It would probably be #2 on my list if I had a different rifle in this caliber. (And 7mm-08 has almost identical ballistics so I have no doubt it would be a great deer cartridge as well)
4. 30-06 in 180gr - I have a love hate thing with the 30-06. It's the only caliber I've ever lost deer with but that was due to bad bullet selection many years ago. I tried some odd 150 gr hollow points that just wouldn't get the job done. But I loved shooting it, killed my biggest deer with it, and the last rifle I bought was another 30-06. It's probably going to be my go to deer rifle in the future but I've got to drop a few with it before I can say for sure.
5. .243 in 100gr. - It just works. I don't why or how that little bullet does such a great job on deer but it does.
6. .30-30 in 170gr (not sure if they still make those?) - It doesn't have the range of the others but it's great in the woods.
I've never shot deer with a .257 Roberts but I would like to get one at some point. I believe it would be a great deer cartridge as well.