Defeating Gnasty Gnorc in the first game will feel this way to most players in their first playthrough.
The first time you successfully ace a speedway may also count.
The fight against Ripto in "Gateway to Glimmer / Ripto's Rage" (name may vary depending on your location), in which you both fight for MacGuffin powerups and proceed to fight it out on a platform, at which point he will create robitic versions of Gulp. Then after that Ripto will sink the platform you're fighting on and jump on a cyborg bird- you promptly get a powerup and give chase, dog-fighting all the way. To say nothing of the mini-games that follow.
The End of Gateway to Glimmer. Moneybags refuses to give back all the money he's taken when Elora tells him to. Elora issues a calm command. Hunter sits on him. Crowning moment for both of them.
There is one where you can play as Sgt. Bird and fly around Enchanted Towers, giving a Curb-Stomp Battle to any enemies in your way, while completing the regular quests. (This option will likely be available after you've completed the level the first time round, though.
Super Bonus Round from Year of the Dragon. Full stop. The amount of gems you get in that level is staggering and satisfying.
If we're listing that, Gnasty's Loot from Spyro the Dragon also has to be mentioned, for the same reasons as SBR.
Sheila, Sgt. Byrd, Bentley and Agent 9 get one each upon being released by teaching Moneybags a lesson in their own unique way; kick, rocket launcher, club and laser gun respectively.
Hunter saving Bianca from a renegade monster in one of his first Badass moments in the "Hunter's Tussle" cutscene.
Bianca, after finding out the Sorceress' true intent, finally snaps back her and storms off to rescue Hunter. It becomes apparent that she only put up with her Bad Boss because she thought she had good intent to save them all. When she didn't, she told her to stuff it.