L4D seems very finicky with stripping the cheat flag from commands. I was fooling with it earlier tonight, and on one map, I could strip the cheat flag from the "give" command, but not the "z_spawn" command, and on the next, I could strip it from the "z_spawn" command, but not the "give" command (this was in-between server restarts, so it wasn't something where the flag was already stripped).