Can be picked up by things other than creatures, vehicles and the pointer.
Can be picked up by the mouse.
Can be activated using the mouse - otherwise CLAC and CLIK style events don't get sent when you click on the agent.
When set on a vehicle, it will automatically pick up things dropped in its cabin.
Creatures don't see you - applies to ESEE and STAR on creatures, as well as internal creature code.
Agent floats relative to the screen. Move it with FLTO. If you call FREL, the agent will float relative to another agent instead of the screen.
Will collide with room boundaries, according to its PERM.
Agent falls with proper physics, including gravity, air resistance and friction. Otherwise, it simply moves with velocity.
Agent can't be seen on a remote camera (PAT: CMRA) or photograph (SNAP). For vehicles, the contents is shy as well.
When set on a vehicle, it allows creatures to see and activate its passengers. The default behaviour is that they can't.
When set on an agent the various rotation commands (SPIN, ROTN, AVEL etc.) can be used.
An agent with this attribute set has a circular physical presence in the world and receives Impact script callbacks.