Guide Voodoo Doll - Spawns the WOF (which is laggy)
Holy/Unholy Water and Hallow/Corrupt Seeds - Modifies biomes (can be used to grief if not handled carfully)
Dynamite, Explosives, Sticky Bomb, and Bomb - Easy griefing tools
Sandgun - Shoots sand (can be used to grief)
Lava Bucket - Easy griefing tool
1/3/5 Second Timer - Can be hooked up to pumps to automate water/lava flow causing grief.
Dart Trap - When too many are shooting at the same time, dart traps can cause lag.
Invisibility Potion - Used to troll PvPers
Inlet/Outlet Pumps - Used 90% of the time to transfer lava or water to where it's not suppose to be. (inside other's homes, on top of homes, on bare land, etc)
Tombstone - Can be placed and edited in protected areas.