When playing custom Garry's mod maps, I find it quite annoying to have 3/4 of the items being the big bright red error prop, meaning that I don't have that thing in any of my owned games.
I do own Portal 1 and 2, L4D 2 and TF2, so I'm guessing all that stuff comes from Half-Life, that I do not own.
Is there some way to download all of these without buying HL and/or HL2?