Flags
1 : Only Break on Trigger - This entity will only break when it receives an input.
2 : "Break on Touch - This entity will break when collided with.
4 : "Break on Pressure - This entity will break when pressure is applied to this entity.
512 : Break immediately on Physics - This entity will break when it hits the ground, if it is attached to a physics entity.
1024 : Don't take physics damage - This entity will not break when dropped with physics, no matter what.
4096 : Start Asleep
8192 : Ignore +USE for Pickup
16384 : Debris - Don't collide with the player or other debris
32768 : Motion Disabled
65536 : Use Preferred Carry Angles
131072 : Enable motion on Physcannon grab
262144 : Not affected by rotor wash
524288 : Generate output on +USE
1048576 : Physgun can ALWAYS pick up. No matter what. [Episode One Update]
2097152 : Physgun is NOT allowed to pick this up. [Episode One Update]
4194304 : Physgun is NOT allowed to punt this object. [Episode One Update]
I think only 1024 would be a good choice, prevents breakage.