If you're the sick type that enjoys scaring the living daylights out of innocent strangers, the spontaneous spewing of frightful cold air surely belongs in your collection of horror. The Ankle Blaster Air Cannon actually does only one thing: it fires a blast of air at ankle length for 1 second, through a ½ in. pipe, and at 110v and 100psi (max.) of constant air supply (compressor). But if it's skillfully hidden, it could be used in many scary ways.
According to its item page at FrightProps.com, the Blaster is designed to mount to single or double-sided haunted house panel systems, usually hidden in unexpected places. It can be used individually, or bought in an all-in-one wood crate.
There are also five different options for activation: An AC power cord, a PIR motion detector, a 17x23 pressure mat (when a poor soul steps on the mat), a repeat timer (at up to ten minutes intervals), and a good ol' hand trigger. All five options are over $300. Enjoy the frightfests tonight.
Ankle Blaster Air Cannon [FrightProps.com via Chris Null's Blog]