Get a Stealth Tank and then go to enemy base and hide in the back. I then come out of hiding only to run over other players. Especially the higher priced ones. Really annoys someone to get 1000 credits and spend it on havoc only to get him run over as he is leaving a building. I have been yelled at and cursed at by the players in question for this tactic. It hurts their economy.
Another tactic is add a nuke into the picture. Place the beacon and (as said before in a previous post) run over any hotwire's engies coming to disarm. this tactic is tricky because as GDI I have stolen several stealth tanks from people doing the exact samething. However I let them plant the beacon then I run them over and disarm the nuke. Yummy points then.
Still another tactic is wait off a common path to my base in a stealth tank (funny how even the most veteran players still use the same paths over and over) and when that slow moving Mammy comes along I get in behind him and start shooting. Yes I have wasted more then one 1500 credit mammy with a ST.

Kai