The first panels of "Titans" and "Kinda" directly evoke the "Oh? You're approaching me?" confrontation between DIO and Jotaro.
"Comparisons" has Orion comparing a bunch of stuff he and Max are doing to JoJo to the point that it also doubles as a Shout Out to the "Is that a JoJo reference?" meme.
In "Transformation", Noah getting himself fully erect involves a Super Saiyan-style powerup, complete with yelling.
"Crisis Averted"'s first panel shows someone being knocked out so hard they ended up in a crater in the ground exactly like Yamcha. This is repeated in "Razzlin" when Vanitas, after looking like he's doing a flying elbow drop onto Max and Cricket, is shown in the next panel lying on the floor in the Yamcha death pose.
In the CheapoMart story arc, Hashim gets "hangry" and screams "Rip and tear!"
Darcy's behavior and speech patterns take a lot of cues from Darkseid, but this is the ultimate example. Her family are all based on Darkseid's associates, as well. She also takes cues from Thanos, at least in "Infinity", right down to having a gilded strap-on with studs that look like the Infinity Stones.
When Adelie is trying to explain to Max that Izzy was cloned in "Triplets", Max compares it to The Clone Saga.
"The Pit" that is frequently referred to is partially revealed, and seems to be just a normal prison, but per Word of God it's very similar to the prison Bane was held in.
In "Penalty Game", Noah informs a concerned Izzy that there's no rules in Arcanus: The Widening against applying dangerous penalties to matches. She responds by saying that she didn't know "the Air Budclause" applied to mutilation.
The leader of the music club in Max's school is an Expy of Colonel Kurtz from Apocalypse Now.
"Rave" features a girl in red fishgirl cosplay and wielding a dual sided yaoi-paddle. She's called "a Fangirl Menace". And just to take the reference even further, "Derivative" has Max and Cricket face her with giant blue and green glowsticks.
"Vani's Angels" is a send-up of the intro to Charlie's Angels, with Vanitas as Charlie and Brittany, Calixta, and Kavya as the Angels.
Music
"Volume 5: Floridian Feeling A.K.A. Waiting for Aliens" features a number of references to the Mountain Goats. The CD Izzy steals from the record shop in "Freefall" and listens to with Addy in "Only Existing Parachute" is their album Full Force Galesburg. The Volume's title and themes reference the demo song "The Day the Aliens Came (Hawaiian Feeling)" from Come, Come To The Sunset Tree.
The description of Darcy's Maximum Profit Equation explains that it can create a product so popular that it achieves complete market saturation.
Pro Ass Fishing gets an AR expansion entitled GO Ass Fishingnote also the title of the strip, complete with extremely lifelike fish girls...and third-party external hardware.
Hashim: So Izzy's on a cocaine-fueled bender. The last time I saw her she'd watched five hours of PBS and then ran off screaming. Sarah: Is it ever a normal day with her? Hashim: With the Izz'? No way! *Izzy crashes a bus through the wall* Izzy: BEEP BEEP CLASS! TIME TO CLIMB ON THE MAGIC FUCK TRUCK!
Arcanus: The Widening is a combined reference to Magic: The Gathering and Yu-Gi-Oh!; it has a lot of mechanics that play like MTG, and when Noah competes in a tournament, players use a phallic take on Yu-Gi-Oh's Duel Disk device.
Sarah's fellow clowns feature a few. One of the female clowns looks to be a Juggalo, as her face is painted like the guys from Insane Clown Posse, she's wearing the "Hatchet Man" on a necklace, and is giving the horns. Another clown looks like if Ronald McDonald's makeup took cues from The Joker.