How good a sale we talkin' here? And, what are you investing in Valve or something?
Almost everything in the store is on sale. There are bundles of indie games with five games in each going for $5. Discounts range from 30% to 90%.
I've bought so much already this month...
I'd recommend Super Meat Boy for anyone who even remotely enjoys platformers.
Yeah, Super Meat Boy is great. It's incredibly hard, but also very satisfying when you finally figure out how to beat each new level. All the levels are fairly short [between 10 and 20 seconds for a quick run], but there's all kinds of pitfalls and spinning blades to make things interesting. At $3.75 it's a steal.
Here's the full list of games currently on sale:
http://www.steamgamesales.com/