Like many here, my wife and I carry-on regs and my photo gear. If I had a can light, I'd carry that on as well. basically anything we'd prefer the baggage handlers not get a chance to toss around.
A word of warning though - based on recent flights, it seems very common that carry-ons (roller bags, not personal items) are regularly gate checked. if you've got anything you deem particularly fragile, you might want to opt for whatever your airline's version of priority check-in is. We just flew United to Bonaire and EVERYONE in the later boarding groups were required to gate-check carry-ons. Made for an awful lot of grumbling given that 90% of thepeople boarding were likely divers.