The Warners driving Satan insane to the point that he throws them out of Hell and into Heaven.
Wakko going crazy angry (as in "volcano erupting from his head" crazy angry) on Ms. Flamiel.
The Warners' defeating the dictator of Dunlikus in "King Yakko", even after their troops completely abandon them. He said he wanted anvils, and he sure gets them.
Just about anytime the Warners enlist the help of other Animaniacs characters, such as Slappy in "The Sound of Warners" and Mindy in "Lookit the Fuzzy Heads".
Wakko's two-note song.
Dot fools Snow White into falling off the tallest castle tower.
The Warners pulling a seriousBreak the Haughty on Myles Standish because he tried to kill their turkey.
The Warners get abducted by aliens who attempt to dissect them and proceed to mess with the alien who was leading the dissection, trap him on his own operating slab, and escape to drive the other aliens crazy.
Slappy and Skippy
Slappy busting out of the hospital to save Skippy in "One Flew Over the Cuckoo Clock". That's incredibly hard to do in real life.
Slappy flying in with Steven Spielberg on a giant UFO in "Three Tenors and You're Out" and beating the Three Tenors (who are heavily delaying the start of the baseball game Skippy had been looking forward to) at their own game.
After peaceful methods to resolve conflict prove entirely useless, Skippy takes a leaf from his aunt's book and schools the schoolyard bully.
The Goodfeathers blowing up a plane in "Dough Dough Boys" by tricking the pilot into flying into a war balloon.
Bobby beating Pretty Boy Robin with one hit, just moments after the latter had subjected him to a No-Holds-Barred Beatdown.
The Goodfeathers tricking Ralph into wrecking Plotz's car, all to "Ride of the Valkyries".
The Godpigeon halting traffic just by casually stepping into the street.
Usually at the end Pesto takes something Squit says wrong and beats him up. But in one cartoon its reversed and the calm and easy going Squit is the one who beats up Pesto
While in most cases Chicken Boo ends up being incompetent at what he's supposed to be doing or unmasked before he can even do anything, in the "The Good, the Boo, and the Ugly" he actually succeeds in disarming the outlaw he's sent to fight and defeats him in combat!
Rita beating up a Nazi dog in "Puttin' on the Blitz". Twice!
The nuns about to beat up stingy tightwad Flaxseed (a candy store owner), only to be reminded they can't resort to violence since they're religious figures. So they proceed to pray, which is immediately followed by the Notre Dame college football team arriving and pummeling Flaxseed for them.
Head Nun: Our prayers have been answered!
Buttons saving Mindy from a zombie horde by doing the Thriller dance.
He gets another one at the end of "Astro Buttons". After being scolded yet again by Mindy's mother, and after Mindy clones herself, he snaps, packs his things, and quits, effectively forcing the neglectful mother to shape up and be a proper parent to her cloned daughter(s).
Katie Ka-Boom's dad showing at least some backbone in the face of his daughter transforming into a monster when he refused to budge on the issue of prom night, with (monster) Katie actually asking "please" in regards to her curfew and her father willing to budge a little. That episode probably had the least amount of damage done in any of the Katie Ka-Boom episodes, saved for a broken chandelier, and the use of stock footage of the house caving in during the end reprise.
Any time the Dover Boys get an appearance. They're bound to get in some delicious snarking (in song!) towards the episode's antagonist.
Runt saving Rita and the other animals in Les Miseranimals where he gets a group of poodles to dig and defeats the villain in the process.
Although he did save Rita from being sacrificed in Home on De-Nile, which shows he's not always gullible.
Also, he saved Rita from being drowned in Witch One.
Back when the show was still producing episodes, Animaniacs fans would gather together for an event called Animania. They mostly prepared screenings of specific episodes whenever they got the chance. However, way back in 1995, a select group of fans were brought over for a gathering at Warner Bros. Animation and the result was Animania IV. It just goes to show how much the production staff cared on the show.
Skippy's dialogue is pretty impressive when you consider that his VA was about seven years old when the character debuted. This is especially notable in "Woodstock Slappy" and its "Who's On First?" gag.