It should take place in a war-torn city, about the size of one of the areas in GTA IV, and Colossi pop up in different areas one-by-one. You could get picked up and dropped over locations by helicopter, or by foot. No guns, but for coop I would like to see one guy with a b*st*rd sword, and the other with like a hand-held ballista. I would like to see the guys running thru nearly hollowed out buildings and timing their jumps onto the Colossi. Some of the Colossus would even climb high buildings or burrow under the sewer system, etc. For coop, the other person would find a vantage point and use something to reveal the weakness from afar. Things would be destructible, giving each encounter a difference in how to take them down and from where. Just a couple ideas.

Edit: Oh, and I would like to see some kind of co-op traps.

Starcraft: Generals (where the maps are planet-sized)

B.C. (bring it back as an MMO please)

Need For Speed: Traffic (as in drug traffic between borders so you could have different police forces after you, or more like Transporter)

Equilibrium MMO

Carmageddon: Last Run (houses are destructible now)

Crusader: No Reason (No Regret and No Remorse were the other two)

SimStuntman (haha)

A First-Person Medieval Siege MMO

Monster Tycoon

Swat 5: Organized Crime Team

Silkroad is pretty good if you don't mind the lag from PC vendors scattered all over cities. It is grinding, but what MMO isn't.  Its good because although not every character may look different, their skill and weapon choices are all up to personal styles.

9Dragons I have just played this week and I really like it.  It is totally just grinding and simple quests, but its true strong point is the kung fu.  You may start as any clan of kung fu, and all differ in martial arts styles and weaponry.  So you don't just level up, your skill and how you choose your path is whats important.  Its pretty new still, only one server, and there will be clan battles later on.  There is already a bond among clan members, which is good because in the long run, you should all want to stick together. Its free now, but it could be worth something later.  As long as nobody ruins the game from within, 9Dragons is worthy of being an MMO.