Source: Dungeon Masters Guide

Siege weapons are designed to assail castles and other walled fortifications. They see much use in campaigns that feature war. Most siege weapons don't move around a battlefield on their own; they require creatures to move them, as well as to load, aim, and fire them.

Siege Equipment
Ballista
Cannon
Suspended-Cauldron
Mangonel
Ram
Siege-Tower
Trebuchet

Setting Specific Siege Equipment

Dragonlance

Source: Dragonlance: Shadow of the Dragon Queen

Dragonlance Siege Equipment
Boilerdrak
Gnomeflinger