Off top of my head, these are the things that most surprised me over the past 25 years:
Resignation of Pope Benedict. Lesson?: God knows.
9/11. Lesson: They hate us, they really hate us. Also that modern evil does not always rely on half-assed emotion-based strategies.
O.J. found not guilty. Lesson: Race relations is, was, and always shall be fraught.
Blue dress with DNA. Lesson: One person's trash is another's souvenir.
Catholic apologist's Bud MacFarlane's marriage. Lesson: religious orthodoxy does not guarantee much.
Episcopal Prevarication: Lesson: Put not your trust in princes (of the Church)
Media Corruption post-Trump: Lesson: Flee to conservative media, fast as you can!