we holler like "HOOOT" or stomping floor. Sometime I drop heavy object make a floor shaking thump. (do that at home, not in public place). Other time I just throw object at my wife's or my friend's "eyeshot" to get attention.
At my work, I instructed my co worker to shoot me rubberbands to get me attention or throw stuff within my eyeshot or tap my shoulder. I even told them to do a "buddy" system to get me in case If I was walking away and one of coworker holler for me, tell other co worker who are close to where I am to grab or stop me 
To get an attention:
Buddy system
Flashing lights
Shoot rubber band
Slam door
throw objects to their eyeshot, not on body
Thump the floor
drop something heavy on floor (That gets attention big time)
camera strobe or strobe (Either Xeon lamp or Superbrigt LED)
Tap shoulder (gently, not hard!!!)
Grab shoulder gently
Wave hands
Act like you saw something spooky, walk toward something that you saw a "ghost". Everyone looking at you and at the wall, You turn to them and smile and tell them I'm getting your attention. (done that 
That give everyone chill on their spine for nothing )
Bang table (not hard but just bang)
Shake table or chair
Roll something to their eyeshot
Ect.. to get them attention without hurting them
Don't need to be drastic.
That's all I can think of
Catty
