Vajra
Vajra is a Sanskrit word meaning both thunderbolt and diamond. As a material device, the vajra is a ritual object, a short metal weapon - originally a kind of fist-iron like Japanese yawara - that has the symbolic nature of a diamond (it can cut any substance but not be cut itself) and that of the thunderbolt (irresistible force). http://en.wikipedia.org/wiki/Vajra
Vadzrapani holds one.Notice the lasso it represents the shen-rope:
And this is Vajrapani gandhara (on the right) holding a flywhisk:
These flywhisks are very sacred as they represent the thunderbolts:
Here the flywhisk in ritual procession in egypt:
http://z13.invisionfree.com/THE_UNHIVED_MIND/index.php?showtopic=14789&st=495