Keep in mind, each of these items has a reason to be banned/changed/nerfed.
Chunk loader: All chunk loaders are disabled.
Spot loader: All chunk loaders are disabled.
Rain Maker: Forcefully changes weather on the server.
Nothing banned, but do note that any item that can move spawners has been disabled. If there is an item that we've missed, please let us know at http://www.serendipitymc.com/support. If caught with a spawner, the spawner will be removed and the appropiate punishment will be administered.
SPAMR ammo: The SPAMR bypasses protections.
PortaSpawner: Moving spawners causes performance and balance issues.
Chunk Loader: All chunk loaders are disabled.
Sacred Rubber Sapling: Sacred rubber saplings can bypass Towny/LWC and cause significant server lag.
Tank: This tank causes major server lag issues.
Luggage: Luggage poses a number of security, reliability and performance concerns.
SDX: SDX has significant Towny/LWC bypass capabilities.