At my brother's wedding:

Pen/paper - constantly in use. I was part of the wedding party and had all the minor details (like who I was partnered with, schedule, etc.) jotted down in mini composition book. Also, a good opportunity to show off your nicer pens. What's the point of being a gear junkie if you can't show off on occasion.

LM Micra - no use. But, a tuxedo is a perfect place to carry that classic pen or Barlow knife.

Fenix E05 - Critical to have this. Escorting my kids to the bathroom (many times), taking motor mouth (son) outside for a cool down (many times), hauling rear down a dark, unlit driveway, in the rain, to get to the shuttle (large school bus), illuminating the inside of the shuttle

Hanky - It was a warm day. And, of course, the kids.

Earplugs - I did mentions my kids, right!?!

What I should have had:

Moleskin and pocket sewing kit - Thankfully the ladies were nicely prepared for the expected wardrobe problems.

Flask - Not for whiskey, but for water. It was a warm day.