My Nord just wanted some mead,
Got alittle to nasty with one of the waitress there serving said Mead because she would not serve me any because I am poor, got hit by waitress for trying to touch her to many times, I get angry because I am sober and looked like a fool getting hit by the waitress so I hit the man NEXT to her to hard in the face breaking some bones, guards hear the commotion,storm in and arrest me:( all I wanted was some Mead...

He caught his wife in bed with two other men....And a woman. Killed them all, dropping his catch from the woods on their naked bodies, blood mixing with blood. He decided life was no longer worth living, and the murders caused quite a stir. When the guards came to arrest him, he slaughtered them. Eventually he was taken down by a strange force from within him...His conscience. He turned himself in the next morning, blood still staining his clothes and dried on his unwashed hands. A strong urge within him tells him he exists for a reason and must find the reason by any means.

Now THAT atitude deserves execution! Steal some mead, drink some skooma...i mean come on guys nobody will execute you for that!Think of something more creative!

She is a graduate of mystic and extremely deadly Black Mountain Ninja (or may be the Sand Dogs Desert Hashashini ).
She has been sent to kill a vey high ranking official i.e. whoever is the TES IV Emperor equivalent. In order to enter Skyrim she has stolen a jewel and let the guards catch her.
Then in prison she receives a letter from her Teacher - the ancient Ninja Master in which he explains that thereis a treachery and betrayal within the clan and her priority is now to protect the target at all costs.

now she can begin...

I picked up a good friend's fork, meaning only to admire the intricate designs. My friend felt compelled to call the guards, who were there instantaneously. Having no Septims on me at the time, I was hauled off to jail, where I stayed in captivity for 200 years.

He tried to block with a one handed sword during a pub brawl

Hmmm...

While drunk, got in a fight with nobility/royalty(they started it!), and of course due to their higher place on the hierarchy and connections and so on, ended up getting an undeserved harsh sentence.

My character was arrested and sentenced to death for using a feature he didn't like, thus violating Skyrim's "Don't like it, you don't have to use it!" law.

well my character is a son of a high standing dummer noble. Get kicked out of the house and forced to eat human. Then jailed for cannabalism

Shrug. No room at the tavern.

He is the suspected Don of a large criminal family.

Because its a crime to be as beautiful as I am.

Because he was an idiot -- and got caught

He was about to be executed because the whole of Skyrim was fed up of hearing him complain about Steam.

For being immune to magical and physical damage, getting bored, then killing everyone in Cyrodil

... because I chose to. I'm just that badass.

My Breton Mage was down on his luck and managed to straggle into Solitude. With no coin and barely enough talent to defend himself he took to doing street shows and he found this to be a decent paying job. The crowd wanted something new so he bought a scroll containing a very powerfull spell with all of his money thinking that if he could pull that of he would've cemented his position as top entertainer in Solitude! He neared the end of his show and prepared his scroll and...! Pronounced the last sylable wrong as he was looking at one quite attractive young woman and immolated many of the crowd. The official body count is at 13 as of now...

Mira'ili, Dunmer, Frost Scythe (for the sake of argument I am listing the custom class here even though it is not a class mechanic in the game, I will still RP her as one..... make sense?... )

The Frost Scythe is a magic wielding assassin like class. They use the ice, snow and environment to aid them in their assassinations. Mira'ili, the great-great... great? granddaughter of my Oblivion character, is in prison on purpose. There is someone there who needs to die. So, if you were to ask the arresting guard, she was caught stealing food and is being held for the night. What she was intending to do was break out of her cell in the middle of the night, kill the target and then go back to her cell, and await her release in the morning.

This plan will be interrupted, I am sure, by what ever events start the game.... but then there may well be a slim possibility that I can actually pick one of the random NPC's in the prison, kill them, get away with it, put my character back in the cell and then move on with the beginning story line. That would amuse me to no end.....

He (Nord) killed the hero of Cyrodil!!!!!! bwahahahahahaha!

My Female Khajiit, while high off skooma, was given a quest by a bunch of rats to fix a Dunmer problem.

My character was imprisoned after, in a fit of jealous rage, he murdered everyone in Riverview for never inviting him to their parties.

My character chose the wrong side in the civil war, and is now being executed by the other side. I think it would be cool if they would start it in one of two places where you have to chose a side during character creation, which will determine which city you start the game in. That would add more depth to your character, I think.

I'd tell you, but I'd have to kill you.

Threw a pie at a Guard.