Get comfortable and go to the bathroom because he gave us a lot to work with. Starting off:
The entirety of the co-op that Tatsu did with The Khold One on Super Khold World. From the very first video where Tatsu gets angry at Khold for bypassing the first couple of levels using exploits that only he would know about to even the preview where Khold dies to the very first enemy in Super Mario World and even part four where they find out that referencing a conversation from Metalocalypse helps progress.
...and then there was everyone's reaction when he led the Tank right back to everyone else:
Officer Bomb: OH MY GOD! WHAT DID YOU BRING UPON US!
In episode 5 of Left 4 Dead, both Tatsu & Corn were on their last down when Sedisp started randomly shouting "Oh fuck, fuck, fuck, fuck!". Tatsu says "What is that noise?" Corn walks around and immediately gets smacked by a Tank, the thing that Sedisp was freaking out about. Later, Tatsu is in the safe room when Sedisp starts yelling. As it turns out, a bunch of zombies and a Tank were chasing him. Then when Sedisp opens the door, Tatsu has a minor Oh, Crap moment and quickly shuts the door.
When Corn gets locked out of the safe room by Sedisp and Officer Bomb during the first campaign of L4D 1 leading Corn to shoot his way in.
Corn: Who's the bitch now?!
Tatsu was waiting throughout the entire Dark Carnival portion of the LP for Coach to say "If I ever find a Burger Tank in this place, I'mma be a one-man Cheeseburger Apocalypse!" When he finally said it, it happened to be in the right situation (No zombies attacking the group, no commentary whatsoever). Tatsu was really happy.
Tatsu:*speaking in a Southern accent* You ignorant bastards, I will keel you!
During the L4D2 No Mercy LP:
After the others reach the safe house, Corn stops short to go smack a toaster off a shelf. The horde enters causing Corn to laugh and force him to fight to the safe house.
Corn: You'll never take me alive! *gets Jockey'd* Ahhh!! *laughs*
Which leads to:
Tatsu flips out after Zoey (a bot at 0 HP on last down) mysteriously starts teleporting and then rescues Corn from the aftermath of being a Jerk Ass.
Corn: I got saved by an angel. *starts laughing*
Which again leads to:
At the very beginning of the next mission, Corn kills Zoey point-blank much to the surprise of Tatsu.
Tatsu: Holy sheet. You're a monster. *gets out health pack*
Corn: *laughing and then gets healed by Tatsu* And now I'm getting healed for it. *resumes laughing*
The Bioshock 2 LP, just...all of it.
Examples include the first Spam Play vid to feature the 'Nipples' conversation, Tatsu getting stuck on one gathering spot for almost an entire video, and this little gem...
Corn: *after DocSigmabot (long story) sodomizes a corpse* Apparently she was a virgin!
Tatsu: *pauses game because his brain broke*
Early in the Resident Evil 5 - Lost in Nightmares you would need to pull a switch to raise spikes in a small room. Corn waited until the last moment to pull the switch. "That switch. Right there. Pull the switch. Pull it. PULL IT. PULL THE FUCKING SWITCH."
During a stream, Tatsu and Corn gave the viewers an incentive to where every $10 dollars that they donated, Tatsu & Corn would sing a song. As it happened, one of the choices Corn made was It's Raining Men.
During Halo 3 we have this charming little exchange in which Corn possibly crosses the Stupidity Event Horizon:
Corn: We're always fighting the Covenant and Popcorn (Nickname for the Flood)! Can't we fight like...you know...aliens?
Tatsu: *pauses the game* ...
Corn: Uhm...I mean...
Tatsu: YOU'RE AN IDIOT!
Both Tatsu and Corn getting progressively disgusted by the PRON Folder in the Harvey Birdman Game. For good reason, it's Prawn porn. Every time he accidentally returns to the area with it, he leaves post haste.
Corn: Roses are red, violets are blue... where am I?
The entire QWOP video, which had Khold sitting in on Tatsu playing QWOP with Corn in the background. Corn probably busted a gut somewhere in there.
Tatsu streamed the ending of Persona4, the grand finale included such gems as a deadpan 'Aw, she was pregnant' when his favorite female character was one-shotted by the final boss and a mighty cry of "FUCK YOU NETHERRRRRRRR!!!" during the final cutscene.
One of their most recent snack reviews featured some So Okay, It's Average cookies from Germany, the general feeling of neither disgust or joy just disappointment was hysterical.
"Chocolate CHIP cookies, each cookie only has one chocolate chip."
The Spam Play of Limbo features Corn (who's never seen the game before) freaking out about the giant spider boss and coming to the conclusion that the Everything Trying to Kill You aspect of the game is due to the protagonist being 'Lil Hitler'.
One of their drink reviews has a hilarious discussion. Two words: Jack La Lanne.
Tatsu has now coined the phrase "Jamie Foxx is a white man trapped in a black man's body, trapped in a white man's money."
During Tatsu and Corn's Spam-play of Sesame Street, Once upon a monster they come to a segment where the game records and plays back what they say, naturally they abuse this feature to hell and back, the video is simply labeled Not for children.