Artifact of Doom: The Mystical Keys, which are in the shape of four books. Two known books so far, the Phoenix Book and the Tiger Book, contain encyclopedic information on taking over the world and evil ethics/war tactics/strategy respectively.
Attractive Bent-Gender: Ian polled readers to find out which character in the comic would win a swimsuit competition. After the results were tallied, it was revealed that character with the second highest number of votes ("Red Haired NPC Girl") was really just Hero, the lead male character, dressed like a girl.
Author Appeal: Jones-Quartey was himself an avid console gamer, which is part of the reason he started the comic.
Berserk Button: As per usual for an Idiot Hero, it's a bad idea to hurt Hero's friends in front of him. A DOUBLE bad idea since as an ex-soldier of SEVIL, he was injected with a Super Serum that activates when he's angry.
Brown Note: The Mystic Keys were quite possibly these. At least reading the Tiger Book made Jeff go crazy and turn evil.
Bungling Inventor: the NPC Machine Guy creates a time machine... when he tried to make a toaster.
Cameo: Khrima from Adventurers! appeared in the halls of Eikre's high school in Eviltown. Hero, Cherry and Galgarion made cameo appearance in Adventurers! as well. This is all in addition to the crossover.
Cannot Spit It Out: Cherry has come close several times to telling Hero how she feels about him. But his stupidity makes her question this feeling as much as circumstances prevent her from saying it.
Cerebus Syndrome: though arguably a subversion as the story went back to comedic after an extremely serious comic.
One strip hung a lampshade on some of the idiosyncrasies of video game plot pacing when the heroes were forced to do a lighthearted butterfly-catching minigame but were completely unable to enjoy it, because they were still broken up about a character who had just died.
Chekhov's Gun: Ian J. created banner ads for a game called Retro Mud where he put the RPG World characters in different outfits. Diane wore her mage outfit in these ads. Cherry was depicted as an archer, although her underboob-displaying outfit never made it in. Detestai was seen in a loose skimpy robe/drape thing that was later donned by Feijoa.
Chekhov's Gunman: Early in the comic, Hero and Cherry encounter a viking named Olaf the Unspeakable, but flee. He later appears as part of a Dual Boss fight, and is much tougher.
Contrived Coincidence: Eikre's introduction led to a number of factors that made it look like he was obviously Galgarion in disguise such as him constantly hitting on Cherry, being overly suspicious and wearing a shirt that says EVIL on it. It turns out that he was just a pervert and EVIL is the name of his favorite band.
The Chosen One: Actually three of them. Hero, Cherry and Diane. Long story.
Parodied with Hero who, while he IS someone chosen, keeps calling himself the Chosen One in Langoria, where he isn't. The elves just give up trying to convince him otherwise.
Cliffhanger: The final battle with Galgarion which was on the verge of starting when the comic ended. And the sub-plot of Reka's robots making a time machine to supposedly save her from being killed.
Cutscene: Usually placed at the end of a story chapter, paralleled to the end of a disc on the game. There was an Art Shift to not only color but a more detailed style to ape the fact that console games go from sprites to more elaborate animation for such scenes in games.
Cutscene Power to the Max: Eikre's Top Cut manages to OHKO a boss character the group was having trouble with as his introduction but he hasn't used the move since, and it's acknowledged.
Crouching Moron, Hidden Badass: Galgarion is a borderline example of this trope. He's not exactly a moron, but his tendency to be Affably Evil makes it easy to be surprised by things like when he raided the Mubble villiage and drained the souls out of most of them, including Howard's girlfriend.
Lampshade Hanging: A lot considering the comic's a parody, but most of it is done by Cherry.
This is handwaved by saying that as a Chosen One, Cherry uses her connection to the Tatsachore to see past the bounds of their world, meaning that while Hero can power up his stats and Diane can use magic more effectively, she just gets to notice game mechanics.
Mood Whiplash: Parodied. Just after Reka dies, the heroes have to play a minigame where they catch butterflies - but since they were extremely fond of Reka and she happened to be a party member at the time of her plot-relevant death, they're irritated, annoyed, sad, anything but enjoying themselves.
No Ending: The characters reach the final boss, begin fighting the final boss and then... nothing. As it turns out, the creator just plain got tired of working on the comic and axed it. Considering that there was a just-introduced character, two missing MacGuffins, and a bunch of unresolved sideplots, the ending probably wasn't that imminent anyhow. Doesn't make it any less stinging however.
No Name Given: No one knows Hero's actual name, including Hero, so he just answers to the name Hero.
Never Say That Again: Jim's friend often does this to Jim, in the form of, "If you ever ______ again, I will kill you."
Pimped-Out Dress: Cherry's dress in the Elf village arc, which impressed Hero... with the increased polygon count.
Pointy Ears: Elves of course have them works as a Chekhov's Gun to keen eyed readers in the first strip when Cherry was introduced to showcase she's not human. Though that also could've been a Throw It In by Ian as well.
Powered by a Forsaken Child: Galgarion has a weapon that works like this: he uses it to suck the soul out of one person, then launches the souls as a beam of energy. It does 9999 damage, although it can also cause instant death, or unfortunately, slow and agonizing death. His use of this weapon, and later boasting about having used it on innocent people, including one underling's wife, are the first signs of Galgarion's true nature.
Plucky Comic Relief: Reka's bots, and various one-shot characters, as well as the cast themselves on a rotating basis.
Public Service Announcement: Marlboros (a parody of Final Fantasy's Malboros) are tentacle monsters who smoke cigarettes, wear cowboy hats, use their horrible smoker's breath to do damage and inflict status effects, and keel over dead of lung cancer in the middle of the fight. Eikre suspects that their inclusion in the game was a PSA.
Red Herring Mole: One of the most elaborate examples ever. The comic goes into so many ways Eikre could be Galgarion that it looks like it could be a parody of really, really obvious Moles, helped by the fact that Galgarion's real disguise is so incredibly subtle.
Running Gag: Hero's stupidity, Cherry questioning a lot of videogame tropes, Podder-head's bad luck and his complaining about not having his arm repaired when asked to attack.
Shapeshifting: Detestai, Earl, and Larry can change into cat monsters as their primary power, but Detestai can only perform partial transformations as she never learned how to control herself while fully transformed.
Something Completely Different: In between "discs" of the game, there would be photocomics of the real-life "player" of the game musing on what he'd just played, switching the disc, or making run-of-the-mill "two gamers on a couch" jokes with his friend. These were less popular than the comic proper, and it's theorized that this was a contributing factor in Ian's Creator Breakdown.
Sorting Algorithm of Evil: Cherry is of course the only member of the party to wonder why the monsters are getting progressively stronger as the party travels.
Split Personality: Detestai, whose glasses seem to give her a more evil personality then when she has them off. When she has them on she's hell bent on revenge, when she has them off, she only wants cuddles.
Stalker with a Crush: Galgarion for Cherry. He turned himself into a rose so he could travel in her back pocket and spy on the party.
Stripperiffic: Diane, despite literally starting out as a harlot, isn't as stripperiffic as many fantasy genre females. Like, say, Feijoa. The elven warriors as a whole probably count too.
Un-Confession: Literally uses the Reset Button for this trope. Cherry admitted her feelings for the hero, and then an enemy attacked, Total Party Kill, Game Over. The player loaded the last save file, and all progress in their love life was lost.