Bear Hug: A man once escaped a bear attack when he locked his arms and legs around the bear in a reverse bear hug, which made it confused and it ran off. If you're on your back and the bear is on you, it might be your last resort.
Dirt: Throwing fistfuls of dirt in the air and at the bear can cause it to be confused and disoriented, as well as obstruct its eyes. Start slinging mud.
Jump In: Bears can swim and love water, but they are not down with wrestling large prey while staying afloat. If there's water nearby, get in and go deep.
Go Sideways: Because of the bear's huge upper body and neck muscles, rotating their heads side-to-side is difficult. Keep moving to the side to make it harder for them to see you... or see your attack on them.
Calm The Charge: While it may be the last thing on your mind, calmly standing your ground when a bear is charging can be the best attack deflector. If you get a bluff attack as a warning, stand, wave your hands, and talk calmly to the bear.
Walk: Running from a predatory animal can trigger the hunter, so walk away with purpose. But if you must run, head downhill. Bears kind of suck at going down, but are awesome running uphill. And their endurance is awful, so keep going.
Flares: These serve several purposes - signalling rescuers, lighting your way and scaring off wildlife like polar bears. Take a few.