Voltage gave out slides (sandals) one year and they were a big hit.

If not a good hat/shirt, I generally want:

1. something with utility
2. something I'm not going to mind having multiples of

For your benefit, you probably want: something I'm going to see and use regularly, but ideally other people see me using it too.

I made a list of odd merch I considered making at some point that loosely fits this criteria:

• pocket knife
• lighter/matches
• eye glass cleaner
• candles
• playing cards
• flashlights
• mini desktop games/puzzles