What was your favourite Steam sale?

I was reading this thread and I started remembering how good some Steam Sales were. After a trip down memory lane, I tried to find a bit about my favorite sale and then I found this:

The Great Gift Pile. Does anyone else remember this sale? So many hidden gems discovered and so many games bought just because those pieces of coal you'd get for playing your games. The sale itself was also amazing - so many good flash and daily deals! It's a pitty that some people ruined it for the rest of us by using SAM to exploit the system and get a bunch of free games. No other sale had the sense of camaraderie that I experienced in this one. People were helping each other to get achievements. Dead multiplayer-only games were revived for a week. People were having so much FUN being nice to each other. It was amazing!

It was definitely my favorite sale in a time when they meant more then just -%.

Anyway, here's the obligatory gib

ps: Let me know if I messed up the sales. My memory is not that good and google searches can be deceiving.

edit: Here are the achievements that you had to unlock to get a piece of coal. most of them had a holiday theme. I think some were even introduced in those games because of the event.

edit 2: I'm starting to remember more funny stuff. There was this task to write a review with a simple Portal example:
task However, most of my friends were too lazy, so they just copied the portal example and pasted in an unrelated game they owned. Good times xD

edit 3: I just learned that the reason you cannot get steam keys on HB for 0,01 anymore is related to this sale in 2011:
"Humble Indie Bundle 4 was going on at the same time, and the name-your-own-price bundle included Steam keys for some of the games whose achievements were needed to win prizes. People were screwing over the Humble Bundle by only paying $0.01 and then activating the HB games onto, literally, hundreds of dummy accounts. Humble Bundle was then forced to raise the minimum price for Steam keys to $1.00."
Fucking cheaters! Abusing a charity drive so that they could exploit a generous giveaway. (ノಠ益ಠ)ノ︵ ┻━┻

edit 4: Here's a video showing how it was back then