I once noticed a Jetstream 32 taxiing past the hardstand area I was waiting at. Noticed the kickstand still attached. Even though they were about 100m away, I waved my arms over my head and tried to make a dangling motion with my arm.
Must've worked, because they turned around and headed back to their hardstand area.
I also saw a gable marker get blown off the grass and onto a taixway once, in front of a 737. Did the same arm waving thing and they stopped the aircraft as well. The wind then blew he marker off the runway and I called airport ops to come collect it.
Doesn't take much to be aware of what's happening around you, but I'd rather say something and be told "we know" than watch damage or a smoking hole happen.