A new update for Valve's Team Fortress 2 adds an in-game trading post that lets users purchase new items and upgrades or swap existing gear with other players.
To celebrate the launch of the Mann Co. Store, Valve has also debuted "the largest addition of inventory items in the game's history", a load of item customisation options and some new mini-games too.
Users will be able to buy items by depositing cash in their Steam Wallet. Funds held here can be spent on any Steam downloads not just in the Mann Co. Store.
You can only trade items that you've picked up yourself during gameplay, not those that you have bought in the store.
Team Fortress 2 is famous for its regular free updates and these look set to continue, despite the addition of micro-transactions.
"Our plan is to continue updating TF2 just like we always have, adding free maps, game modes, new features, and more," explains an in-depth FAQ on Valve's website. "The Mann Co. Store is simply an alternative way of obtaining items that other players can earn during gameplay.
"Segregating players into groups that can't play together, based on who bought what, is something we'd like to avoid."
The update is available now for the PC version of the game. Xbox 360 users are still left out in the cold though, with Valve recently admitting "total failure" to update the console version.