Owlor 🦋One of my favorite silly dice tricks is to have tables whose index numbers exceed the numbers you can roll on your dice. There are a lot of funny TTRPG-writing gags you can do with that. Having something absurd as the unreachable entry is an easy gag, but you can also use it to convey that a certain thing exist in the universe, but the player characters are categorically prevented from encountering it.
Another fun dice trick I've been exploring is using exploding D6es for tables (exploding = when you roll a target number, usually the highest, on a die, you roll an additional dice and add the results together.) This creates one set of entries that are common and one set of entries that are rare, but the funniest consequence of this technique is that there are unreachable numbers in the middle of the table and that's extremely fertile ground for subtle game design gags.
Cus like, it's generally pretty obvious that entry number 7 on a D6 table is gonna be nonsense, but it might not occur to someone right away that entry number 6 on an exploding D6 table is equally unreachable.