For General Hunting
The Gunwerks bipod is great for all prone positions. It deploys extremely fast, it's solid, and fairly light. If weight and cost are not as much of a concern, the MDT Lightweight Double Pull is awesome.
Sitting or kneeling, I prefer a tripod.
As some others have mentioned, you can use your pack which works just fine for a lot of instances. I still prefer a bipod/tripod combo for my style of hunting. I prefer spot and stalk or ambush hunting.
If you've ever been on a long crawl, and tried to push/pull/carry your backpack instead of using a bipod you know it can suck. It's also much louder. There is a reason myself and most people I hunt with drop our packs before making the final stalk.
Other styles of hunting may work better without a bipod.