Siren

Sort of surprised I'm the first reviewer of this. It is a great free plugin.

Great for dub and reggae. The delay is very old school and sounds beautiful.

The fact that it responds to pitch info makes it is possible to create melodies within the wild siren effects.

It doesn't sync to MIDI timing but you probably wouldn't want it to when using it in dub/reggae style music.

Simply put, it is excellent all round.