City of Steam -- at least on R2Games servers. The publisher has announced that doors will be closing at 2:59 a.m. EDT on November 22nd. Even with what are probably the most impressive graphics in a browser-based game, CoS apparently couldn't keep enough players to remain viable. With the closure, the in-game currency Electrum can no longer be acquired, but all previously bought Electrum can be spent on store items throughout the month.
Does this mean that CoS is powering down for good? Not according to developer Mechanist Games, which has announced that it plans on releasing a new version of the game the same month:
Circumstances have contributed to a significant loss of players and we've decided to cease the current game operations for the Global English version and take City of Steam back. This is a decision we have taken months to reach, and are confident that it's best for the health of the players, the community and the game itself. City of Steam is not shutting it down. We at Mechanist Games will improve and self-publish the game, and endeavor to make it available to as many of the original fans as possible by cooperating with popular English language browser-gaming platforms (to be announced). City of Steam will be upgraded during the time it is offline to better suit the player demographics of the new browser-gaming platforms publishing the game; new content, new features, new systems, massive change to the economy and statistics, new equipment and cosmetics, new quests and an overhaul of most of the level art and main quests. Some features will be removed. There will also be a massive flying fortress for characters of any level to congregate in. Because of these numerous and sizeable changes, the game will be re-launched in November under the title City of Steam: Arkadia.[Updated with the statement from the press release from Mechanist!]