Unity Layers

Default - Has collision with anything that collides with something else, so no collision with TransparentFX for example

TransparentFX - No collision and not used

Ignore Raycast - Not hit by projectiles

Water - No collision and not used

UI - No collision, used for all non-worldspace UI

Hands

IgnoreRaycast - Not hit by projectiles

Hittable

Reflect - Only used to check if an object should make projectiles reflect

Stick - Only used to check if an object should make projectiles stick

LocalPlayer

OtherPlayer

WorldUI - No collision, Used to render UI in world space

StaticShadow - No collision, only receives shadows from baked lights

NoShadow - No collision or shadows received from baked or realtime lights

StickTeleport - Detects collision from the arrows, but lets the teleporter through

DynamicShadow - No collision, only used for objects which receive shadows from realtime lights