Valve_software is currently artist type for some reason (while Valve_corporation has the right type but isn't in use) but nevermind that; I believe it's customary to tag companies in crossover pics, and we've got Rochelle from left_4_dead here in post #1146767, so which do we use?
Wikipedia notes L4D as being developed and published by Valve Corporation, but if you google for the homepage you get Valve Software. The wiki article for the company itself says any of the 3 work (the third being just Valve, which seems a little too generic for a tag (currently used for the object, but in only one pic)).
I guess I should also ask, how do we deal with bought-up copyrights, like enix? Use most current (square-enix) instead?
Updated by Log