Green Man Gaming (GMG) just put out a new 30% off voucher good on a “range of pc games.” I believe the general exceptions are going to be games with Cashback/Creditback offers.
The voucher is GMG30-DPLIM-DN831
Edit: F1 Race Stars (Steamworks) is $22.40 after the voucher. This game looks like a decent Mario Kart clone for PC. Doom 3 BFG Edition (Steamworks) is $10.50 after the voucher. Apparently it comes with all of the Doom games. That’s awesome.