Two that come to mind for me and in the correct order were:

1. Poison oak leaves
2. Pumice rock when the urge hit exploring a volcanic caldera.

Yours?

PS. No. 1 on the list I didn’t know would be #1 until the next day!

Used.

excluding things that are not actually toilet paper like poison ivy leaves and 80 grit sand paper.

the single ply gas station mega rolls.

the covid TP shortage caught us with the least amount of TP we had in probably a decade.

my wife worked at the farm co-op the office was in the gas station
she had just ordered a case of the big rolls for the gas station when the TP shortage hit so she quick ordered us a case as well.

we made it through the great TP shortage on that case but don't care to repeat.

Wet TP in the outhouse because the roof leaks is also bad worse than the thing gas station stuff.

The TP we had in grammer school in the 60's was pretty bad, had chunks of wood splinters in it, lol

My socks….

Gravel

This certain type of grass in Idaho that if you don't wipe it the correct direction, it has little barbs/hooks in it.

Old sears catalog.

Nobody travelled in the lands where you eat with the right and wipe with the left?

Birch bark (too brittle)
Rolling papers (too thin)
Sawgrass.....yowzer!

John Wayne toilet paper, it's rough, it's tough and it doesn't take crap off of anyone.

pine cone

Corn stalks don’t work real good. If it comes down to that, you might as well just take off your underwear and use that instead cuz you’re going to end up throwing them out anyway.

The kind where your finger breaks thru! LOL

There's nothing wrong with socks. Nice and soft and absorbent. I've never regretted using socks.

There is actually bamboo toilet paper. I get splinters just thinking about it.

Your socks do a good job, but wearing boots without socks isn't fun. When on camping trips, I find it better to use your friends socks, when they aren't looking.

That shiny plastic like stuff in the Asian countries 50 years ago. don't know if it is still around or not. But did not work well for me---ended up using hand wipes.....jk

The kind I don't have with me when I need it desperately.......