World of Goo is on sale for 80% off as the Steam Daily Deal for 10/13.
World of Goo = $1.99 / £1.39 / €1.79
Definitely try the demo, if you’ve never played the game before. It’s really fun.
Edit: oops looks like this isn’t a daily deal. It’s actually a special promotion. Lasts until 10/15.
Steel Storm: Burning Retribution is actually the daily deal for 10/13 at $2.49 / £1.99 / €2.24 (50% off).