Space Engineers is £11.39 on Steam, a 40% saving.
Normally I'm hesitant to run deals for Early Access games I haven't personally tested, but this one's a little different in that you're able to try it for yourself! Space Engineers is completely free to download and play this weekend on Steam, meaning that you can suss it out and decide whether you like it. If you do, then pick it up at a discount. Thanks oli86!
In case you didn't know, Space Engineers is a game about being a Engineer. In space. More specifically, an engineer who builds magnificent ships and structures, then has the option of blowing them up too.