Honestly, I'd have to say Hinata. She went ahead and challenged Pain even after seeing what he was capable of. Sure, it was stupid, but it was pretty damn brave too..
Other examples would also be:
Jiraiya, he sacrificed everything to try and help his village, when he fought the 6pop with one arm ripped off.
Shikamaru, Neji, Chouji, Kiba and Rock Lee, challenging the Sound Four and Kimimaru
Tsunade, when she was going to fight Pain even when she was so low on chakra
Tobirama, battling 20 enemy shinobi, just to help his comrades
3rd Raikage, fighting 10.000 shinobi for the sake of his comrades (makes Tobirama's achievement seem pretty lame lol)
Anyway, these were the first people who came to mind
