Total Annihilation had a really awesome community as far as unit and map additions, which naturally led to some bat-shit insane tactics.
I never played online, just against the computer, just prefacing that.
I can't remember the level, but it was one of the CORE maps that consisted of the bottom having space for three start bases, a loooooooong narrowish bridge up the middle to a fourth and fifth start area.
Didn't matter where the bots or you started, it generally broke down into a race to gain control of the bridge. This is where the Vulcan came into play. It was a four barreled gattling artillery gun, using the ARM's most powerful/long range artie as a base. It had retardedly long range and firepower, but they were vulnerable to aircraft, ate resources like you wouldn't believe, and took forever to build.
However, if you made Vulcan packs of say... 10, 20, 30 cannons in a row, or a block, powered by an obscene number of resource gathering buildings early in the game, by the time you'd had the match going a few hours, they would be picking up kills as the enemy sent hordes of vehicles after you.
A Vulcan with 1500 kills? Can tag stealth fighters and scouts out of the air at their maximum range. 20 vulcans with 1500 kills each can only be taken out by nukes. =D
Also in TA, there was a downloadable battleship, I believe called the SeaDragon. It had a disgusting amount of weapons and armor, but was somewhat limited in that it couldn't go across land to get to anything that was fortunate enough to be out of it's range.
There was a downloadable heavy transport that it turns out could easily lift the Sea Dragon.
Turns out, this dramatically increases the range of a Sea Dragon. =D Of course, if by a stroke of luck, someone managed to tag the transport with anti-air, it AND the sea dragon blew to hell (which was an expensive thing you tried to avoid as much as possible), but something about watching a FLYING battleship made me want to play Steampunk music...