I have several tables of "fluff" for certain types of events. I used to fill up notebooks with that type of thing when I played RPGs regularly. I still pull the material out for RPGs or wargames. So, f'r'ex, instead of rough terrain is -1" movement, rough terrain is draw a card from a deck of business cards (3 or 4 sheets, uaully) I printed with different penalties that averaged to -1" (mostly 0s, -1"s and -2"s) and colour descriptions of the event. Some good reasons for a minor delay in movement:
… trips over his own feet, stumbles and has to get up
… started walking the wrong way, then turned around
… shoe came off in mud.
… foot stuck in a gopher hole.
… branch snapback in the face.
… Hey, guys … I just stepped in … well, give me a second, here.
… aaah. charlie horse. charlie horse. aaaaah. charlie horse.
and, of course,
… stumbled on a rock, lost grip on your weapon, lunged forward to keep it from dropping, fell into a forward roll and came out standing, facing the right way. (+1" movement)
In an RPG a "non-event" where you tell the PCs that "You feel like you're going the wrong way." is a great GM prank.
Likewise, random noises (and sometimes smells added) that either do or do not mean anything are great fun. There should be a pattern, but it should take some time to figure out.
In a sense, most objects (including people that don't actually act in the scenario) are somewhat McGuffins. So a few absurd ones are always good, whether they are to be obtained, escorted somewhere, protected, or destroyed
… compromising pictures of the Agency Director's daughter
… No, that's MY chocolate cake recipe
… the beloved pet that croaks at the end of the scenario, regardless of outcome
… the secret file that turns out to be a handwritten note to return the file by last week
The best example of this is the game Kragmortha. You play as goblins trying to sneak around and steal valuables while not being caught, and cursed, by the Big Boss too many times. When you are cursed, you draw a card that levies a requirement on the player like "Keep your tongue out of your mouth for the rest of the game." or "You have crab claw hands for the rest of the game."