a good tactic that drives the other team nuts is the
"Where the hell is that beacon?" trick.
Yes I agree dumping beacons to have the enemy disarm them will cost you the game. But using this in many situations is very advantageous.
Dump a beacon in your own base right before your teams attack is executed... the enemy freaks out and you have the engies going building to building listening for it... meanwhile your attack is more effective, even tunnel infiltration can benefit from the destraction.
Example: You have a sniper with a clean shot to the enemy base. But the Infantry Barracks is full of engies negating you rushes. Mass a new rush and before the strike have someone decoy nuke.
Engies run out of barracks.
Sniper kills Engies.
Building gets punished.
WARNING/DISCLAIMER: If you are a total n00b and are reading this, do not just do this randomly, it must be done when the situation and team will benefit from it. remember 99.9\% of beacons you place in your own base will get everyone very mad at you for wasting a beacon. IF you are a good player make sure you communicate with your team when attempting this because it MUST be a coordinated effort to take advantage of the panic affect.