In issue #94, Valker said he classifies superheroes in two categories: the ones who (try and fail to) stop gunshots with their hands and the ones who think he won't shoot them. Later in the story he asks Rat-Man what of these two kinds of heroes he is, and Rat-Man replies "I'm of the kind you can't shoot". Classifying Rat-Man as the one who thinks he won't shoot, Valker reaches for his gun... And that's when he realizes Rat-Man stole it before he asked.
Rat-Man versus Il Drago (a Shallow Parody of Goku from Dragon Ball Z). No one had ever succeeded in resisting more than a minute against him, or even scoring an hit. Rat-Man not only resists longer than anyone before (at one point Il Drago started hitting him with a rock and demanded he pleaded for mercy. Rat-Man didn't plea,the rock did), but even hit him square on the nose with a punch. That was when Il Drago prepared his ultimate attack, that would send the victim in another dimension so far that everyone would forget it, but also when Rat-Man had another moment of awesome (this one shared): The Man With The Spider Costume (a Spider-Man Expy), has recovered his will to fight (previously lost after getting mauled by Il Drago) by seeing Rat-Man, and so he first socked Il Drago in the face, and then caused the ultimate attack to hit the two of them. To complete the awesome, Il Drago was forgotten immediately, but The Man With The Spider Costume wasn't.
The end of 299+1, the 300 parody. Rat-man pulled an Ephialtes (by accident and sheer stupidity). But then he comes back and makes a Last Stand, so epic that the Persians run and don't dare to attack with swords but use a Rain of Arrows (against a single man). He gets to not be left behind and joins the Spartans in the march for the afterlife.
Persian Soldier: God Dwarfy! (referencing Rat-Man stature)
Issue 86 and 87. A Darker and Edgier mini-arc about Janus Walker, set a post-apocalyptic world Dream World, specifically Rat-man's subconscious. This "Walker" is Rat-man's memory of his adoptive father. Badass ensues.
Woman: How are you planning to enter Joba's fortress? It's as closed as a fist!
"Walker": Look inside your closed fist. What do you see?
During the same story arc, Rat-Man, for discovering his childhood hero and costume inspiration Mr. Mouse (a Shallow Parody of Mickey Mouse) has created multiple generations of both superheroes and supervillains in the name of profit, is left on the roof of southern one of the Sister Towers (counterparts to the Twin Towers), that is promptly hit by a plane with the other Vendicatopi on board to Kill 'em All. With some prompting from the ghost of his mentor The Bat (the only other superhero who had ever opposed Mr. Mouse), Rat-Man takes the only way to safety to continue the battle... Namely jumping on the roof of the Northern Tower. It's promptly shot into Negated Moment of Awesome when the ghost points out the Northern Tower was on the other side, but without that idiotic error he would have reached it...
Rat-Man is saved by the Fly Man, another superhero who swears to help him against Mr. Mouse. How does the issue end? With Rat-Man's signal projected on a cloud before Mr. Mouse's heliocarrier as a warning he's coming for him. That's when Mr. Mousefinally stops being smug.
Issue #99 is the Grand Finale (the series is slated to end with issue #100, but it will be a celebration issue). Its awesomeness, with the final defeat of Mr. Mouse, is beyond words.
After that, the Mook stood back up thanks to his possession... When he discovered the hard way why Rat-Man was paraplegic: he had rejected his will to be a hero, who had left him and became a gigantic and muscle-bound copy of Rat-Man who always tried to get back into him... And the gigantic Rat-Man was about to try and return into Rat-Man. Cue asskicking andLudicrous Gibs. Immediately followed by Rat-Man accepting the call... And absorbing the giant Rat-Man into himself, reacquiring the use of his body.