How about the one to remember all the necessary plant nutrients?
C. HOPKINS CaFe is Mighty good with some Manganese Cloride. Its so good that the Mob Comes In.
This translates to: C, H, O, P, K, I, N, S, Ca, Fe, Mg, Mn, Cl, Mo, B, Cu.
There you go, all the Macro and Micro nutrients needed by plants.
I had a Lichens class when I was in college and for our lab final we had to ID 50 lichens to genus and species. The one I had the most trouble with was Ocrowlichia tartaria. So, I made up the saying "old crows lick tatar sauce". Now I'll never forget the darn thing!
steve