While explaining the Pilgrimage to Chief, Tali gives him an anecdote about how Kal'Reegar brought home a Brute Gravity Hammer as a gift to the Rayya's Captain. Reegar was reportedly very injured in the process of acquiring it, and when Chief asks exactly how he did so, Tali laconically replies "It wasn't easy."
Pretty much all of Chapter 31. We get a huge battle sequence with Saren's army vs. Forerunner Knights vs. The Flood vs. Master Chief's squad, the first three of which team up to take down Chief and co once he's rescued. They get curbstomped. And then, to stop Saren from getting away, Master Chief performs the Mass Effect equivalent of a Fastball Special, with help from Liara. And to wrap things up, after Saren gets away, the squad madly dashes back to the Normandy with the looming prospect of a radiation induced implosion of the Registry hot on their heels.
Chapter 33: There are Vanguard Hunters now and it's as awesome as it sounds.
They're back in Chapter 38. And kill a Geth Colossus without taking a scratch.