Knytt Underground | IndieGameStand | £0.62 (RRP: £4.99)
First things first: Knytt Underground has been in countless bundles over these last few years. Check your Steam backlog and see if it's there.
If not, you can now pick up this excellent indie platformer for £0.62 at IndieGameStand. It's got exploration, a great aesthetic, neat characters and is basically strong across the board. Again, though, check your backlog.