Something I got from Spoony which I really liked:
“There is nothing there.” -> “You don’t see/perceive anything.”
Even if there isn’t something there, keep the players on the edge and guessing how good their skill worked. And it makes it just a little bit less gamey if the character doesn’t have some divine insight that there really is nothing there instead of deciding that their skills just show that there is nothing there and be happy with that - or not.
Of course, extend that to everything. Pull away from the facts of the game and put more ambiguous language in.
I also like misdirection that doesn’t result in anything.
“And where are you standing right now?” - “Ok, just checking.”
After insight check on an honest npc: “As far as you can tell, he’s telling the truth”
player rolls perception
DM: “you smell the distinct smell of gas building in the cave.”
Player: “I cast fireball.”
DM: “Alriiiiight… As the sparks ignite in your hand, the gas explodes, causing a cave in and burying the entire party under a mountain of rock. Congratulations, you are dead.”
Player: “Why didn’t you stop me?!”
DM: “You failed your wisdom check, dumbass.”
I hate it when the “and this is where we end the session for tonight” part happens 10 minutes in… once had a high level party teleport to the complete opposite side of the map 10 minutes after starting… That is when I learned what high level really meant.
I had a 15 minute session once because I offhandedly gave my players a foldable boat like 15 sessions before. I had intended for them to have to cross a mountain range controlled by Dwarfs who’d ask them to assist with a dragon hunt in exchange for passage.
But instead? Nah, they use boat.
Why, who would believe it? There just happened to be merpeople who has a dragon problem in the sea!
I have to pee I have to pee I have to pee I have to pee
