cdkeys.com and g2a.com i have used frequently in the last year
got ac 4 i think for 9 bucks
mk x for 22 bucks
batman arkham knight with season pass 42 bucks
tried this 5 random steam key on g2a ended up with crap won't do it again only cost like 5 bucks says it's completely random but it's probably limited to poorly reviewed games