QUOTE(mekanic @ 03/25/06, 04:37 AM) [snapback]232234[/snapback]
Would someone please make one, I could sure use it about now.
Sapphire Zap from GenArts will do what you want.
Set the "wiggleSpeed" to 0 and animate the "length" parameter (not branchLength, just length).
You'll probably want to set glowBright to 0 too.
http://www.genarts.com/sapphire-shake.html
They have a downloadable demo.