Most rifles are capable of far more accuracy than the guy pulling the trigger. I have had good liuck with most of my guns: i would recommend looking at Rem, Win, Browning, Savage or Tikka. They all seem plenty accurate given you top them with some decent glass and do your part.

As far as caliber, deer and reasonable distance: 260, 270, 280, 7mm-08, 2506 or mags will do fine(7 rem mag, 7RUM, 300's). Really the choice is yours, just pick a caliber you want, in a style and manufacturer that fits you and top it with some good glass. I bet they will be plenty accurate for yeah. (If you buy factory ammo, then you should look at availablity, choice, etc)

Or get a custom built gun on what ever action you prefer. May cost a bit more but then you can make exactly what you want.

BTW, I think an 800 yard shot on a deer is never required and not something that should be viewed as a channel for you desire to snipe! If you want to shoot those long distances do it on paper, it don't bleed and suffer if you miss by a few inches!