This deserves more explanation. Marlin and Coral are happily moved into their new home, when they realize that their neighbors have vanished. They look up and see the barracuda just.... sitting there. Marlin tries to convince Coral to hide in the anemone, but Coral doesn't listen. She goes for the kids, the barracuda goes for her, and Marlin goes for the barracuda. And for a brief moment, HE HOLDS THE DAMN THING OFF.
We've seen everything everything Marlin goes through in the movie. Nigel relays the story to Nemo, it sounds like something akin to The Odyssey.
The part where Gill saves Nemo from Darla, putting his own life on the line.
Gill: (breathing heavily from the oxygen outside the water) "Sharkbait... tell ya dad... I said... HI!" (plops onto the dentist tools to propel Nemo out of the room once and for all!)
Equally awesome is how Gill got on the table in the first place: he got into the aquarium's bubble volcano and with Jacque's help, used the force of the bubbles to launch himself halfway across the room into Darla's hair (causing her to drop Nemo's bag on the table). Considering that Gill probably got his scars from a botched bubble-cano launch, putting himself in that position again for Nemo is incredible!
When Dory and Marlin finally get to Sydney, only to be swallowed almost immediately by a pelican. Marlin has had all he can take at this point and simply decides in the middle of sliding down the bird's esophagus to fight back.
Marlin:NO! I didn't come this far to be breakfast!
Nemo going to clog the water filter up the second time, even though his first time almost got him shredded to bits. He then gets out, unscathed, much to the delight of the tank gang who thought they were too late to save him.
Dory GETS HER MEMORY BACK!
Gill's first appearance when Nemo is stuck in the filter tube:
Gill: Alternate wiggling your fins and your tail.
Nemo: I can't... I have a bad fin.
Gill: Never stopped me. (he shows Nemo his tattered fin)