In Der Monster Klub, not only does Randy battle against 4 stanked kids simultaneously (and win), he used their attacks to get closer to the object he needed to destank!
Stank Like Teen Spirit: Howard quickly realizing what the cause of the stanking was with Randy and formulating a plan to cure it. Howard's mad chess skills manage to beat Viceroy's specialized robot and curing nearly everyone in the student body. Then Randy disposes of the robot quickly with his Ninja Hot Balls.
Randy Air-Fist punching the Sorcerer in "Raiders of the Last Nomicon"
Not to mention escaping Mc-Fist's lair using knowledge he gained in previous episodes.
Randy and Howard fighting the fused stank form of flute girl and Stevens and getting the Sorcerer's key.
Less awesome, but still so, is Flute-Girl(And several others) dumping Stevens.
Randy chasing after the Magically empowered McFist doom robot, without his ninja suit because it has Howard. When it jumps off the dam, Randy dives after it.
Mac Antfee and Randy battling inside the Ninjanomicon without the suit. In spite of having less experience, Randy beats him by tricking Mac Antfee in to opening the Ultimate Lesson Door.
Howard throwing that cinderblock and temporarily knocking out Catfish.
In a clever move, Viceroy exploits Howard's destructive abilities to find the flaws in his so-called 'indestructible' objects and used them to create an unstoppable robot. Then Howard one-ups him by still helping Randy beat it by luring it to the site where a satellite crashing was bound to happen.
Randy accidental ricochet shot with with Theresa twirling sticks was pretty impressive.
When Randy prepares to sacrifice himself by forcing himself and the Sorceress into the Realm of Shadows, Howard immediately goes and rescues Randy before he becomes trapped as well.
"Randy Cunningham: 13th Century Ninja" Has ton of these.
The Sorcerer showing just how much havoc he can raise when freed, both in the past and the present.
Randy holding his own against the Sorcerer before breaking the Tengu Stone and having it possess Howard. Because the Tengu and Ninja suit are linked, Randy combines his fighting experience with Tengu Howard's might a-la video game style, with the Sorcerer summoning an aura clone to help him.
Then there was the First Ninja himself coming back and saving Randy and Tengu Howard before they along with the Ninja's squire seal away the Sorcerer and undoing the damage.
Speaking of the First Ninja, he has some sort of Mystic DRAGON PUNCH, which Randy asks him how to do it.
Principal Slimovitz and what's left of the Norrisville High student body organizing a resistance movement against the Sorcerer.
The Sorceress 2 had one for both Randy and Howard. Throughout the episode, Randy was bitter because Howard did a last second Kill Steal on the final boss of a video game. In the end, Randy learned a bit about sacrifice and performed a Heroic Sacrifice to stop the Sorceress. Howard, without any personal benefit, jumped in to save Randy from being stuck in the vortex.
Randy and Howard thwarting a Drunk On The Darkside Julian, a user of actual sorcery with one of the oldest fundamentals of magic ever: sleight of hand.
Randy taking on a Stanked Lavendar Hart in a rock-off. Keytars have ever been so Badass.
Randy and an army of Badass Adorable fighting the Halloweenja suit's kids-turned-minions with hugs and confetti in "Let the Wonk One In".
Randy getting to save the day without the suit for once in "Shoot First, Ask Questions Laser" by doing a 'Ninja Mid-air Desuit' and putting the mask on one of the two Laser-bots tracking the Ninja. When the other bot shoots it:
Robot: Ninja destroyed.
Randy:<Emerging from the smoke> That wasn't the true ninja. *blows it up*
After facing it in "Enter the Nomicon", Randy has finally learnt Hydro Hand by "Happy Hanukkah, Howard Weinerman", and its first use is in defeating a nigh-indestructible Yeti-bot.
The final scene of "Snow-Klahoma!". Shadow Julian strolling down the street after dark, whistling as all the street lights he passes blow out, then the power in every building he passes shorts out...