Pronounce and pronunciation seem like they should have the same root, but one of them has an extra 'o' for some perfectly logical reason. I know the difference and don't consistently misspell it, but if I edit a sentence to switch from one to the other without noticing that it's a danger inflection ...
Also maintain vs. maintenance for the same reason.
It's usually not classified this way, but I consider 99 Bottles of Beer on the Wall a New Year's song. It combines two of the main NYE traditions -- alcohol and counting backwards.