Being Watched: Rhea, and others, are able to do this through Maerlyn's Rainbow.
Black Comedy: A joke about a literal dead baby is vital to the plot.
Click Hello: The first confrontation between the gunslingers and the Big Coffin Hunters features a chain of one after another.
Coitus Uninterruptus: Jonas and Coral are having sex when they hear the oil patch getting blown up by Roland's team. They don't stop, because they "had reached the point where it was impossible to stop, even under threat of death or dismemberment."
Karma Houdini: Clay Reynolds survives the events of the story, but the narration lets us know that he was killed shortly thereafter in an unrelated shootout.
Kill 'em All: Even the characters who survive in Roland's story are dead by the time he tells it, except for Sheemie.
Logic Bomb: Faced with an insane but brilliant A.I. that has challenged them to a riddle contest, Eddie forces it to guess the punchlines of bad jokes. It guesses them correctly, but doing so causes it great strain. Under a barrage of them, each more illogical than the last, Blaine finally short-circuits.
"Why did the dead baby cross the road? Cause it was stapled to the chicken."
Mexican Standoff: What could be the most over-the-top straight version ever. Depape holds Sheemie hostage, Cuthbert gets the drop on him with a slingshot, Reynolds points a gun at Cuthbert, Alain sneaks up on Reynolds and puts a knife to his throat, Jonas puts a gun to Alain's temple, and Roland gets behind Jonas with a knife to his back.
Roland, at least relative to Eddie, who cracks too many dead baby jokes. Roland actually gets pretty pissed at Eddie's "ridiculousness" at various points, only to end up apologizing once it saves them all.
Blaine can guess the punchlines of jokes, but he hates the illogical nature of them, to the point that they can become a Logic Bomb.
I could call you a sucker of cocks, for instance, but you have no mouth. I could say you're viler than the vilest beggar who ever crawled the lowest street in creation, but even such a creature is better than you; you have no knees on which to crawl, and would not fall upon them even if you did, for you have no conception of such a human flaw as mercy. I could even say you fucked your mother, had you one. I can call you a faithless creature who let your only companion kill herself, a coward who has delighted in the torture of the foolish and the slaughter of the innocent, a lost and bleating mechanical goblin who-
Red Right Hand: Eldred Jonas has white hair, a limp and a quavery voice, all of which are apparently the result of the traumatic beating he received when he failed his trial to become a gunslinger. His failure is probably the reason why he's such a scumbag.
Shout-Out: The climax directly recreates the climax of The Wizard of Oz.
Traumatic Haircut: Rhea hypnotizes Susan and orders her to cut off her hair after losing her virginity. However, when she tries it, Roland stops her.
The Western: "Is it a Western?" "All Roland's stories are Westerns."
What Happened to the Mouse?: At the end of the flashback, Roland's mother gives him a belt. He promises to tell his ka-tet the story of how he lost the belt, "for it bears on my quest for the Tower." Whether he tells the ka-tet or not, he never tells the reader; the belt is never mentioned again either in the main series or in any of the side materials.
Your Mom: Eddie to Blaine: "Sticks and stones may break my bones, but words will never hurt me. Or, as we used to say back in the neighborhood, 'You can rank me to the dogs and back, but I'll never lose the hard-on I use to fuck your mother.'"
Roland to Blaine: "I could even say you fucked your mother, had you one."