cel shading in a render, and ingame celshading are worlds apart,
that and im not sure if real cellshading is actually possible in the half life engine,
for a render you just have to click a few times, for ingame effect it would have to be coded in, and i wouldnt think it would be easy
well its just faked... in real to make it ingame celshaded you will have to copy the whole model( doubled polys). So it will be damn laggy
we should start banning people for even mentioning that technique and cel-shading in the same topic,