It pains us to have to kill another Half-Life 3 rumour, it really does, but it seems even more likely that the third Valve announcement this week will be all about the gamepad for Steam Machines.

Valve is set to give us the third piece in the puzzle tomorrow (the THIRD announcement? Half-Life 3 confirmed!) and there's been another hint that Gabe and co will be introducing a controller designed for Steam Machines.

In its Steam Machines beta test agreement, Valve makes an explicit reference to a controller (or perhaps several) that may complete a busy week of announcements.

"Valve Corporation ("Valve", "We", "Us" or "our") has developed and produced prototypes of entertainment system hardware and software, including a set-top box running custom software and a game controller (collectively: "Beta Products")," it states.

Gabe's in control now

There was already a hint in the FAQ section on Valve's site stating that "Steam and SteamOS work well with gamepads, too" and telling us to hold on tight for more "very soon on the topic of input."

While this sounds a bit like SteamOS will be open to existing gamepads, the reference found in the agreement makes it sound more like Valve will be offering up its own controller option(s) tomorrow as well.

So not too long to find out. Then again, maybe Valve could treat us to some Steam-exclusive software as its "one more thing". Half-Life 3? Left 4 Dead 3? Portal 3? We'll take any of them.

Here are all the essential facts on Valve's Steam Machines