When I was in New Orleans I met a girl who wanted to play vampire. It's good if the guy is getting tickled because the rules are you can't resist the vampires movements, so you can say... cover your ribs with your arms, but if she takes your wrist and pulls it away, you aren't allowed to resist.
Also, you can play a game where one person is tied and torture tickled for about five minutes, then the other person has to go through it, add five minutes to every round. See who can go the longest without giving in. Whoever holds out longest gets to tickle the other for the rest of the night, but playfully, that way, if you can't take it, you can give in to receive much lighter play. It gives a reason to submit.
Not sure if those are really scenarios.. I tried to come up with a few, but they just came up more as characters. I'm sure you've done the tickling for information, let's see.. oh, alright, got one that's more of a game than a scenario but here goes.
Usually I don't have a lot of trouble winning a tickle fight, so one girl I was dating wanted to make a game where she had an advantage. We called it the Knight and the Thief, the Knight has a crystal crown for the princess, and the thief wants it, the Knight can't drop it or it might break so he has to hold it at all times, you can hold anything doesn't really matter as long as it isn't too light. Eventually she started using an old scarf of hers to try to tie my legs up. It's a lot of fun if you have a lot of space to play.
Hope any of that helped.