Hm. Well, the Avengers RP is pretty much out; I fear I've been "comic-booked" to death over the years, and fanfic of that sort leaves me rather cold. The same for the football player scenario. All of my athlete characters start to blend in my mind after a bit.

Historical, now... I am an amateur history buff (as if the Puritan role-play we're in doesn't give you enough warning.) Here are a few ideas just to throw out at you in that vein:

1) The First World War - A German Zeppelin is shot down over the English countryside after a bombing run on London. The only survivor is a badly wounded airman who must depend upon the good graces of the Englishwoman who finds him and starts to care for him.

2) The First World War (fantasy) - A US citizen who felt he could not let Germany's atrocities go unanswered, he joins a Canadian regiment at the start of the war to find himself in France. By 1916, he's seen his share of horrors yet managed to survive. Now a sergeant, he finds himself trapped out in No Man's Land during a nighttime raid, the rest of his raiding party slaughtered. German artillery starts a barrage as a the enemy prepares to charge the English trenches and he's caught right in the middle. Then he spies a woman in white who seems completely out of place. He manages to drag her into a crater just as the shelling starts and saves her life. As the shelling stops, she abruptly vanishes. Throughout the rest of the war, she appears to him when no one else is around. They begin to form a reluctant relationship, one strained by the fact the he knows she's hiding some sort of secret. (Who she might be is left to you: time traveler from the past or future, figment of his imagination, visitor from an alternate timeline, etc...)

3) World War II - The Nazis complete their occupation of the Netherlands. A German Major from the Wehrmacht has been retired from the lines due to wounds (he walks with a cane), and has been given the job of co-ordinating all of the various organizations to make sure things run as cohesively as possible (Waffen-SS, Gestapo, Luftwaffe, local government officials, Dutch Nazi sympathizers, etc...) Due to staffing problems, he finds himself forced to draw upon Dutch locals to supplement his clerical pool, including a rather pretty young secretary. What he does not know is that it is her recently-deceased uncle's mansion that he has been given to as his residence and offices. What he also does not know is that she is Jewish.

4) Civil War Era - A "cannaller" and his crew on the Erie Canal become caught up with the Underground Railroad and reluctantly transport a pair of escaped slaves and their female conductor from Albany to Buffalo. While they are aware Federal marshals and slave hunters are probably on the hunt for their passengers, it seems the conductor has some forgotten to mention that she is wanted as well... and the person who wants her back will spare no expense for her return.

5) Prohibition - Double Dan is down on his luck. It most likely has something to do with always betting double or nothing. Having lost far more than he's won at the racetrack, he doesn't have an ever-loving dime in pocket. Not a plug nickel. Or a wooden one for that matter. After a really bad loss at Saratoga, he hoofs it to Buffalo in the hopes of placing a last bet that'll save his neck. Only, not having the scratch to place any more bets, he is forced to roam the streets and avoid being picked up by the gendarmes. When a young lady dressed to the nines is attacked in the alley he's sleeping in, he comes to her aid. Turns out, this doll is the widow of a pretty high roller, and she now owns a little speakeasy that is also down on its luck. A rival gang is making things tough for her, and she needs whomever she can get to help turn the tide. (This is sort of a cross between the webcomic Lackadaisy and the stories of Damon Runyon.)