I really like diagrams that are on triangles. I think they're very clever and bring three concepts and their intersection or relationships together in a beautiful, easy to understand format. the pyramid versions of triangle diagrams are also good for layering things most to least! A very versatile shape! (it is also my favorite shape...)

The soil texture tirangle is such a well known classic. Once you know how to use this particular diagram, it works super well! Are you more sand, clay or silt? let me know. personally, I might be silty clay loam purely based on vibes.

gotta love the velocity formula triangle as well. It was really easy for me to mix up the orders in my head as a kid in physics so this saved me!

The pyramid of sound was a huge part of my music education and I have a particular fondness for this diagram. Where do you fit in with the band? Are you too loud? Too quiet? consult the pyramid of sound! I used to look at this pasted inside my music folder every rehersal :).

Ok so I don't actually know too much about heirarchy of needs but I think its neat and the various memes of it that go around are really funny. I will make my own and put it here!
I also really like this speedrun to meet all of its requirements done in 8.1 seconds here!

The feldspar triangle is a little weird and it truly does not use all of its real estate but its ok i love her anyways <3