Depends on what you wanna do, how long you're gonna do it, how many hours a day your gonna do it, and what level you want to start at first. Hunting doesn't make money until 68 Red Chins. For fishing, some people prefer fishing for monkfish, some prefer lobsters, and others prefer sharks. It all depends, you must be more specific. Can't determine on what you're specifically asking. Additionally, if it's specifically toward a 99 skill, then Hunting and red chins in my case. That's what I would do.
But still, be more specific....