I usually play "normal", but sometimes I engage in psychological warfare.1. Mad rushes. On field, keep buying grenaders and rush into the Nod base. You can always hit the obelisk with 2-3 grenades before it zaps you. It drives the Nod guys CRAZY when they constantly hear the Obelisk firing and "Nod obelisk under attack". Usually it drives them so nuts that they stop all their plans just to watch the tunnel, leaving them open for an APC rush. If they put proxy mines I just run through them and come right back with another grenadier...its a free unit and they dont get much points for killing me. If I have money to spare I will buy a gunner and attack their airstrip from the other tunnel.
2. Misleading messages - I will fake an "accidental" message to all. If you are Nod you can send a message to all saying "only need 1 more flame tank and then we rush". This will definitely put GDI on the defensive, and they will all gather near their base entrance and buy mobius's in expectation of a flame tank rush. Then you rush out from tunnel and plant beacons which they usually dont disarm because they dont want to trade in a 1K mobius for a hotwire
If not anything it just shakes them up...if they are attacking they will often retreat to get ready for the rush.