Project still as-of-yet unnamed. Oh well.
One of my all time most played games is Team Fortress 2, and with good reason. Valve took the classic Quake mod and turned it into a beast of a game, perfectly balanced with a great community and constant updates which only serve to make the experience that much better. I've convinced friends to buy TF2, I have bought it for more than one person myself. A thousand hours total or so later, it still manages to entertain me.
What keeps people coming back? Is it the game itself? The community? The achievements? The updates? The unlocks? The latter of the bunch is probably the most true, because of one simple thing that Valve added to the game. Hats.
In May of 2009, Valve released a huge update, adding new weapons for the Spy and Sniper, and, announced at the end of the update, the first nine hats. They were a gimmick at best, and served no real purpose, but as time went on, more hats were added. People used programs that simulated idling in an actual TF2 server to acquire more hats, so Valve added an extra, free hat for people who didn't cheat to get their hats. People asked for more hats. Valve added more hats. As time went on, people wanted to trade hats, so Valve finally added a trading system with the Polycount Update, as well as adding the Mann Co. Store for microtransactions and some new hats which have added effects for wearing a full set of Polycount weapons plus a hat.
At first, I didn't want anything to do with hats. They were stupid, nothing but a small change in appearance, most didn't even look that good.
Then I acquired my Brigade Helm.
It was my first hat, save the Cheater's Lament, and it was for my favorite class. Of course I had to wear it. So I did. Then I had more hats drop. Then weapons, which I crafted into metal to make hats. I had hat fever. In the TF2 server I played on, I was known as a lord of hats, and someone who would make fair trades of a hat for any other hat, so long as I didn't want the one I was trading away. This slowed down eventually, as I got settled in with the hats I had. Hats stopped being an issue, but I couldn't help but feel a bit of nagging greed every time someone opened up a crate in my presence and received a hat, or even worse, an unusual hat. Most of the unusuals don't even look that good, but I didn't care. They were rare. I wanted them.
To this day I still have no unusual hats. To this day, I don't care enough to try to find one, nor do I have the income to do so. It is entirely obvious Valve has created a Skinner Box just for people like me, who want the rare stuff, the best stuff, no matter how stupid it actually is. Hell, I will willingly return to that Skinner Box for years to come so long as the game continues being fun and the community continues being great.
I still know, however, no matter how much I play, that I'm only still playing because of the hats.