Cleopatra calling Caesar out on his sabotage of the palace construction.
Dogmatix, drinking a life-saving drip of magic potion in the Asterix in Britain movie. Bulldog-asskicking ensues.
Obelix (while de-aged and no longer has his Super Strength in Obelix All at Sea) sees Asterix get knocked out. This results in him growing back to adult size and strength. Ass-kicking ensues.
In Asterix and the Roman Agent and The Mansions of the Gods, when the villagers get over their quarrels and proceed to kick ass. There's something deeply satisfying in watching the bunch getting their differences fixed by busting fools.
In the former, after completely annihilating all four Roman camps at once (and the Pirates, who were just passing by), they give Tortuous, the man who caused conflicts between the villagers, his just deserts: they act like he was their double agent, with gifts, cheers and all. Cue the Roman General sending him back to Rome with the accusation of high treason.
Whenever Cacofonix gets invited to the big feast at the end of the book, instead of being hogtied as always. Because it always happens if the bard did something utterly badass, intentionally or not. Just to name a few examples:
In Asterix and the Normans, it is Cacofonix' singing that finally teaches the Normans what it is to be afraid, and also inspires the first display of bravery by Vitalstatistix' nephew Justforkix (who actually enjoys Cacofonix' singing). Not only does Cacofonix attend the banquet, he gives a musical performance while his usual tormentor, Fulliautomatix, is the one tied to the tree with parsley stuffed in his ears.
In The Mansions of the Gods, Asterix and Obelix cause one of the couples in the eponymous block of flats to leave, then give the flat to Cacofonix. His singing causes the entire block to empty; when the legionaries from Aquarium are moved in and Cacofonix is forcibly evicted, the Gauls use this "slight" as an excuse to demolish the entire building. Cacofonix is invited to the banquet as a show of gratitude for his role in the scheme.
Obelix's birthday in Obelix and Co. They got him a whole camp full of brand new Romans, for Jupiter's sake. While they stood in the background singing "Happy Birthday", too!
In Asterix and the Twelve Tasks, Asterix's meeting with Iris, the Egyptian magician. It has to be seen. It eventually ends with Iris short-circuiting his eyes and hypnotizing himself into believing he's a wild boar. He runs out onto the yard to the previous people he hypnotized, believing themselves to be a cat and a bird.
Asterix:(seeing Iris' glowing eyes) That must be useful for reading in bed.
In another Task in the same movie, Asterix cleverly deals with the unhelpful Bureaucrats of the House that Drives Men Mad (Obelix himself almost goes insane) by fast-talking a couple of desk clerks into looking for a document that doesn't exist, which causes a chain reaction to the other office workers leaving their posts to look for it throughout their own insanity-causing maze of a building. Thanks to Asterix's plan of using their own attitude against them, the entire building's workforce ends up running around, mad as hatters.
Not to mention that the only sane person (whom they met earlier during the search) happens to have the permit that Asterix and Obelix are looking for and reluctantly gives them the permit, only to realize his foolishness and go insane as well.
In yet another Task from that movie, Asterix and Obelix are challenged with eating everything put before them by the Great Chef of the Titans. A menu that includes: a cooked flock of geese, a herd of lamb, a full school of fish, a fully roasted ox, a cow, veal (because separating families wouldn't be right), a camel, a mountain of caviar (with one piece of toast), and an elephant. A whole elephant. One Gilligan Cut later, the Chef bemoans the emptiness of his kitchen, while Obelix is asking why he left before serving the main course.
Obelix: Did anyone see where the chef went? He walked out and I only have me starters.
Related to above, when the duo entered the Cave of the Beast and confronted it, it Smash Cuts to a pleasant city where they found Caius Tiddlus who asked what the Beast was like. Obelix replied, "Very tasty". Obelix ate an Eldritch Abomination.
Asterix's angry ranting to Roman ghosts in one of the tasks because he and Obelix are exhausted after the tasks they've already completed and they need a good night's rest. The ghosts end up scared of him.
In Asterix and the Laurel Wreath a Roman slave has our heroes thrown into prison for attempted murder of Caesar, then winds up "ab-so-lute-ly blotto" in a pub. Asterix waking him up, paired with his reaction, is the stuff of legends.
In Asterix and the Actress Obelix punches Asterix in a temper and Getafix gives Asterix some magic potion, thus causing Asterix to go completely insane.
Asterix and the Cauldron ends with the pirates, of all people, enjoying an unexpected windfall when the eponymous cauldron filled with Whosemoralsarelastix's hoard of sestertii falls into their ship.
Vitalstatistix gets one in Asterix and the Big Fight. Challenged to a duel by a traitorous Gaul chief with both of their villages at stake, Vitalstatistix finds himself in the fight WITHOUT a magic potion, as Getafix has suffered memory loss. As such, he spends the beginning and middle of the fight fleeing from his opponent. When Vitalstatistix learns that Getafix has recovered and there's magic potion to go around, the chief of the indomitable Gauls instantly wins the fight by One-Hit KO. Without pausing to drink said potion.
In Asterix and the Flying Carpet, Cacofonix brought a drought to end, saving a princess in the process, by singing
Also a funny moment, but in Asterix in Corsica, the corrupt, and oppressive Roman leader was ready to abandon his soldiers to the Corsican rebels. When the soldiers find out, they decide to bring him to the front lines. Literally, they put him directly in front.