As goofy as Trigon's Bumbling Dad persona is, it is actually quite clever how he used Raven's friends to try to convince his daughter to be a Demon Spawn. It just goes to show why Trigon is considered the source of all evil. Fortunately Raven isn't stupid.
Beast Boy tricking everyone in the end. Taking out the context of them all dying and becoming ghosts, it's pretty awesome to trick the pranksters by going along with their prank only to then turn it on themselves.
The Titans have an incredible battle using a Humongous Mecha against Gizmo's giant robot army.
Not to mention Robin beating Gizmo with just a the left leg, with his upgrades to match.
Starfire turns out to be a surprisingly effective villain in "Starfire the Terrible". She blows up the moon and while her evil lair is made of cardboard, it has real lasers and a robot army that gives the Titans a hard time.
Robin and Cyborg accidentally combine their attacks to create an explosion so powerful, it can be seen from space.
Bonus points later for trying to combine other things, the first thing they try? Robin's cane and Cy's Jukebox, and the combination Works
Once Raven realizes how awesome her legs are, she gives them quite the workout. Just ask Jump City's villains.
Robin, Starfire, and Raven's trio in "Waffles".
Remember in "Super Robin" when Robin wore himself out beating Mammoth? Well, while infiltrating the Hive as Red X, he effortlessly beats the crap out of him!
Everyone's dream...well maybe except Beast Boy's dream in "Dreams".
Cyborg's voice and the Titans' dances in "Grandma Voice".
The Titans battling the Puppet Wizard during the season 1 finale to get their souls back.
Starfire's revenge on Blackfire during the end of "Mr.Butt".
Even better is that the girls' portrayal is more similar to that of the 1998 cartoon, with Blossom's intelligence finally being showcased, Bubbles' Badass Adorable tendencies outright taking hold of her situation, and Buttercup actually being badass instead of having Spotlight-Stealing Squad tendencies like she does in the 2016 cartoon.
Robin gets a moment of awesome when his ability to listen to the narrator clues him in on Mojo's trap so they could plan in advance.
Beast Boy becoming an even better ninja than Robin in "The Art of Ninjutsu".
Robin's been getting a lot of these, lately; there was the Easter episode where he found out that Santa Claus had been kidnapping holiday icons, including the Easter Bunny. Looks like the writers finally remembered that Robin used to be Batman's ward.
The Pig Latin speech that Robin gives in "Obinray".
Robin:Iway aymay otnay ebay away igpay. Utbay Iway amway away anmay, andway ymay ownway anguagelay aymay ebay uglyway andway udecray, utbay itway isway away anguagelay Iway eakspay omfray ethay earthay.Iway askway ouyay ymay othersbray andway isterssay otay andstay ithway emay againstway ethay inesway oppressionway. Onlyway ogethertay ancay eway eakspay ethay uetray anguagelay ofway isthay orldway…. Eacepay.(Translation: "I may not be a pig. But I am a man. And my own language may be ugly and crude, but it is a language I speak from the heart. I ask you my brothers and sisters to stand with me against the swine oppression. Only together can we speak the true language of this world…. Peace.")
The ending of the five-part miniseries "Island Adventure", with the Titans fighting most of the villains that they've encountered in the series so far, and using Control Freak's props against him.
The tip of the iceberg is when they have other classic DC Comics villains appear at the end. To summarize, the Titans' little stunt pulled in Sinestro, Penguin, the Joker, Harley Quinn, General Zod, Solomon Grundy, Bane, Gorilla Grodd, Poison Ivy, Mr. Freeze, Darkseid, Two-Face, the Riddler and SLADE! The last one deserves special mention, because, even if it's for a very brief moment, Slade kept getting name-dropped throughout the series, and it's only now that he finally makes an actual appearance!
The Titans are actually very competent as villains.