Guild Wars 2

These would be solo and/or group instances in the racial cities that could be accessed at any time. They come in multiple flavors:

Survival-
Survive as many waves of enemies as possible.

Speed Mission-
Complete the mission in the fastest time possible.

Scored Missions-
Obtain the highest score possible in the allotted time.

Combinations of the above.

There are, of course, many possible variations on all of them – including, but obviously not limited to: point defense and/or capture, sabotage, jumping puzzles, running supplies or other items, scavenger hunts, etc.

These missions, while cooperative in format, are competitive in that there is a daily leaderboard for them, with the top x players receiving a prize via mail at server reset.

Similar challenge missions were in Guild Wars 1 in Factions and Nightfall. They could be an excellent way to bring some life into the cities or random outposts in the explorable zones, as well as provide some interesting endgame options.

I enjoyed the CM’s in GW, so two thumbs up from me on your idea.