EF_BRIGHTLIGHT
From Valve Developer Community
EF_BRIGHTLIGHT is defined as 0x002, or 2.
This effect creates a dynamic light with an RGB value of 250 250 250
and a random radius of 400 to 431 at the origin.
Usage
To use this effect, turn off SmartEdit mode and add the following keyvalue pair to the entity: effects 2
.

Remember that you can set the effects value during runtime using an entity's AddOutput
input with the input value effects x
(x being any summation of effects flags to enable).
Warning: Using the AddOutput functionality for this, the new value may interfere with an entity's simulation functionality.