ASP - Alert Whistle
All whistles are definitely not created equal. ASP Whistles are molded from ordnance-grade polymer, and feature a Spanish cork ball that generates a piercing tone of incredible intensity. Whether for training or traffic control, there is no more effective means to signal a command.
The Alert Whistle is available with or without a tooth guard (select from drop-down above), and is also available with a neck lanyard here.