You probably already know this at this point, but the Steam Summer Sale has begun. The theme, this year, is Steam Summer Picnic Sale. As far as I can tell, it has no relevance other than it ends on July 4th. They do claim to have 12785 titles on sale, though, and filtering all on-sale software by Windows lists 12595 of them.
Some interesting deals include 40% off DOOM, 50% off Fallout 4, 35% off Rise of the Tomb Raider, and 50% off Just Cause 3. The Witcher 3 is also 50% off, although it was like that before the sale and its DLC are still basically full price if you want the both of them. If you're looking for older titles, Assassin's Creed IV: Black Flag is 75% off, as is Civilization V and Sleeping Dogs: Definitive Edition. As always, have a browse if you are okay with tempting your credit card.
If not? … … Sorry.