I had some ideas because I do enjoy stuff like Jrose but it gets boring after a while. These are both run ideas and things you can do for fun
>how good is X's team? (Use npcs team)
>glitchmon runs
>out of bounds exploration
>breaking the game with action replay
>trying to find new glitches (still tons to find and document)
>unconventional special/physical attacker runs (physical gardervoir, special machamp, offensive shuckle, etc)
>spin off games. Mystery dungeon is really fun
>how fast can X pokemon clear the game? Kind of like casual speedruns
>Actual speedruns, theoretical speedruns if you're extremely autistic
Lately, I do my modified oaks challenge, or like a Master run. Catch all available mons up to each gym, bar level evolutions up to gym leaders ace level (you wouldn't have to evolve slakoth until wattson, or seleo until Wallace) and have the pokedex nearly completed by your first hall of fame entrance. Post game legendary should be your last entry. There is also a level cap for your team up to gym leaders ace, and you can only battle them with the number of their mons. Lastly, try to have the most money you can by your completed dex, no items in battle, animations ON, shift OFF, talk to every npc, explore every area, collect every item, hack in every event if possible, and have this all done at a steadfast pace. And this is just the region dex btw, none of that national crap. No nuzlocke rules either, they're not fun.
It's pretty much just beating the games in their completion with some arbitrary rules to keep you from breaking the game with items or grinding. I did this for entries I don't like and it usually makes me appreciate them more.