Trimming ear hairs.
Ear hair is one that has impacted me as well.
A weird feeling is finally being older than most professional athletes. As a kid, they always seemed like they would forever be older than I, but even now I find myself thinking of them as older. Like U.S. Football players, I still can't reconcile that I'm older than most of them, it just seems strange.
Granted I'm only early 30's, but the one moment that was crystalized for me as an "I'm old" moment was at a concert (Pigface) a few years ago. Chris Connelly came out and performed a RevCo song from 1990 and more than half the audience had no idea what it was. The place went dead except for a handful of old-timers that went ape to hear such a classic performed live.