My ignorance is based around how it's pronounced, not how its spelt. I read prodigiously, i might see a word i have read semi frequently and still be pronouncing it incorrectly in my head. I am loathe to use such words in conversation and prove to everyone I'm as stupid as they suspected, albeit as I age I do care less in that regard :)

Last one was about 8 years ago, misanthrope.

The other thing that crops up occasionally are words pronounced differently based on regional variance. I was watching an Attenborough documentary and he used arc-a-pell-aa-go and I use arc-a-pell-ego

My gf agreed with me (we're Australian), now I pronounce it the same way Attenborough does , much to my gf's annoyance but in my defence, it's called English, so I defer.