Gimmicks - most of them don't work except one or two days out of the year. Usually the same day your wife makes you cut the grass or your boss demands you work or loose your job.
The only one I really liked was the doe bleet can.
Rattle bags, grunt calls even deer decoys can do as much to scare a big deer away as it will attract them.
Just think of it in human terms. You been living in the same neighborhood all of your life. You know every tree, bush and animal for a country mile. Then one day, out of the clear blue, this big old buck sounding noise comes from out of the bushes.
What do you do? Stand your ground like a man, or do you run like a day old Popsicle in the sun. YOUR BEST BET IS TO SIT REALLY STILL AND NOT LET THE DEER SEE MOVEMENT. DEER HAS REALLY GOOD EYE'S AND THEY CAN SEE MOVEMENT A REALLY LONG WAYS OFF. THEY DON'T HAVE TO SEE A ENTIRE PERSON TO GET SCARED.
ALL THEY REALLY NEED TO SEE IS SOMETHING THAT DOESN'T BELONG WHERE IT IS AT. You start rattling a bag and the next thing you know the buck is headed for the next county.