Gluh, flashing tail lights, amirite?
I'm not sensitive to general flicker, but this example comes to mind as I notice it every time, and it's a potential safety hazard!
Very cheap LEDs do it too, because they're only lit half the time. Less than half, actually. Same as some failing fluorescents (when they're flashing, not just making that lumpy fluctuation).
For lights that plug into the wall and are lit less than half the time, in principle you could power them by DC and be done. I don't know how safe that is. You certainly want the output fused and limited.
For lights that are installed and driven by a controller (like tail lights), the lamp itself could smooth out slow pulsing, but this affects turn-on/off speed, which might not be a good idea with regards to, say, the safety of brake lights. This would require an inline module to be designed, and probably an extra power or ground wire to be ran. So, not too cheap/easy, unless done in quantity.
Tim