Things I've actually used to harvest big game and love:
30-06 or 308 - 150 or 165 AccuBonds. Runner up 165 or 168 Nosler Ballistic tips in 308, and 180 BTs in the 06.
Tikka 7x57 - 175 ELD-X, because it's crazy accurate in that gun (3/4 MOA) and Accubonds are not (1.5 MOA). Early testing with the 162 ELD-X looks to shoot even better (first 10 rounds into 0.65 MOA, dam!), will try those next year.
Note: 140 Accubonds were my fav in my old Savage 7x57, and to be fair, I prefer their on game performance to the ELD-X.
303 British - Winchester Power Points (killed more big game with that bullet than any other except Accubonds).
Things I own but have never personally shot a big game animal with, but would without hesitation:
45/70 - plain old 300 grain Interlock HPs.
338-06 - 180 AccuBonds
223/5.56 - 55 grain Hornady SP w/c.