Mine is that I always crouch before stealing something, no matter if anybody's around or not

I put every corpse in the nearest fire.

I don't wear my helmet around 'people' (non-hostiles).
I always get on my horse from the left side.
I say, "I'm sorry, Brother." every time I kill a dragon.

I crouch curtsey style before speaking to the local Thane and Jarl.

I had a really bad habit of searching every container I ever saw in Oblivion. Every barrel, every box, every chest. I just couldn't resist.

In Skyrim I can't stop making new characters. I've made over a dozen characters already and haven't gotten past level 40 with any of them. Trying to tone that down and just focus on one or two.

In FNV I opened EVERYTHING...skyrim not so much, I usually know what's in a barrel..few potatoes, cabbages, or apples

Grab every ingredient from every plant I walk by, even if I know I don't need it.

Whirlwind Sprinting into walls, objects, people...

Strange things happen.

I whirlwinded into a cooking pot after I first got it and buzzed a few feet above the ground for a good two hundred yards until I let go of the shout. Probably could have kept going if I held down the shout too, but now I keep trying it everywhere trying to repeat it.

I save my game progress every ten seconds in Skyrim.

Leaving food,wine,books,weapons,armor etc at religious shrines or places which look like memorial altars for the dead.

Kneeling to the Jarl or other persons of a higher station. Not the Thalmar though since they're snobbish cretins.

Not taking gold from a corpse if theres only one coin on them so they can pay Death for the boat ride across the river styx or wherever people pass on to in the Elder Scrolls.

Always giving charity to beggers.

Not acttacking an enemy right away to see if they are hostile or not eventhough i may have been acttacked by the same species before.

Not eating raw meat unless am playing an Orc character.

Not eating food during combat. I will drink something though if i have the chance to temporarily break away from a fight and get behind a wall or door etc.

Mostly avoiding swimming in huge expanses of water but will still do it when fishing and clam diving or checking out a sea wreck.

Eating at least twice every day and drinking after doing something strenuous.

Making sure to have mead or ale on hand to share with the tavern drunks

Playing almost whole one to two hour game sessions doing nothing but talking to npcs and hearing their very interesting stories. Cant believe i like the conversations so much i dont mind being in a dungeon alot of times.

Searching every nook and cranny of a dungeon to see what there is to find.

Showing mercy to surrendering bandits only to have them heal up a bit and acttack me one final time.

If I kill someone alone in a house/building, I will drag the body into the fire. If I'm near a cliff or bridge I will throw bodies off of it.

When people die in that strange position where they're on their knees, but leaning slightly backwards but remain upright, I reposition them to be lying flat. It's creepy the first way.

I try to do that silly run/jump dance up the sides of mountains for a bit before actually looking for the path up.

I grab all the food I can becasue i'm always low on health potions.

I take off all apparel when children are present.

If an NPC is sitting down and there is a free chair I always sit down before talking to the NPC.

I'll often throw dead people's bodies into a lake/river or over a cliffside/down a staircase. I pick every plant I come across, and half the time forget to make potions. Even with no acrobatics skill, I jump constantly.

If an enemy is particularly annoying I'll strip them down after I've killed them.

I hoard food even though I never use it.

Same with alcohol.

If I see a sweetroll it is mine.

In Oblivion, I stole forks. The first time I did it for a laugh, and then the guard came storming in, demanding a massive 1 gold bounty from me. After that I felt it was a matter of honor to steal them. I would RP my character has having been caught after going on a massive fork stealing spree, and thats why he was in prison at the beginning of the game.

I remove my armour when i enter water.

lol I do the exact same thing, it creeps me out when I see dead bodies in that position and I love seeing bodies fall off a big cliff.

I have an obsession with collecting a lot of different items, sometimes for no practical use.

I pickpocket arrows from every guard I come across. I have a terrible thirst for arrows.