Valve is holding a Steam sale to celebrate Halloween with many of the titles on sale featuring horror elements. Valve will use any holiday as an excuse for a sale. There's an INCREDIBLE number of titles discounted at least 25% off, with many offering 50% to 75% off their normal price. We've compiled a list of all of the co-op titles you can acquire. Weep for your wallets ladies and gentlemen, weep for them.