@Lightingeye60: yeah definitely agree with you on that, greened out useless MV lamps.
Flickering LEDs is one of the worst.
I'd say when I see a row of MH lamps all with different color changes is terrible.
Yellowed and cracked refractors are very annoying.
As an electrician I like to see all lighting working correctly and properly maintained.

Battery lanterns that underdrive and kill fluros.
People leaving batteries in said battery lanterns and corroding the insides.
LED Christmas lights that look like a gaming PC exploded on your tree and flicker to give you a seizure.
Glary LED lighting.
Seeing an unusual sight and not being able to snap a pic.

@Lightingeye60: yeah definitely agree with you on that, greened out useless MV lamps.
Flickering LEDs is one of the worst.
I'd say when I see a row of MH lamps all with different color changes is terrible.
Yellowed and cracked refractors are very annoying.
As an electrician I like to see all lighting working correctly and properly maintained.

Another lighting pet peeve of mine is using a wattage above the maximum wattage rating (such as the use of a 100W incandescent bulb in a 60W maximum fixture or using a 150/200W incandescent bulb in a 100W fixture). That’s one of my bigger pet peeves because the use of a higher wattage than the rated maximum can actually be a fire hazard.

As well as use of incandescent bulbs in LED or CFL only ceiling fans.