I think that if you are going to take a center fire rifle I'm under the opinion that it should be a .223 Remington, and you should use FMJ ammunition. This would give clean holes in all game, and while it may not give the fastest kill, it will certainly preserve more meat on smaller animals. The .223 Remington is not the most powerful cartridge on the planet, but I know that it can kill the largest game, especially in real life situations where you throw trophy collecting out the window. As far as the make up of the rifle itself I would pick a sturdy bolt action with a synthetic stock and a stainless barrel. There would be iron sights on the barrel, but I would also advocate a good quality fixed power scope. If you looked at something like a Remington Model Seven stainless synthetic with a Leupold FX model scope I really don't think that you could go wrong.