Borealis
N5X6R-YC6K3-6RCWZ (I may have used this already)
I also have steam keys for these that I'm pretty sure haven't been used. Message me if you'd like one.
Humble Bundle 3
Galactic Arms Race
Enclave
SpaceChem
Dino D-Day
Really Big Sky
Zeno Clash
Litil Divil
Borderlands 2 Campaign of Rage RMNQ-5ANC-AD6R
These might be UK only:
Velocity NQ9R-99NP-DG74
Breakquest DJGE-H9ND-M5T8
Canabalt P46L-88NE-B9AP
Wizorb ABJT-Q3NL-533R
PS+ 30 Day 69E4-A6NQ-6GC2
I'm not sure if any of them work