Since there (sadly) is no compiled bug thread (but if it does exist, maybe someone can point me in the right direction), here's a few I just encountered:

Horses:

Cannot be sold or hitched or told to "Sit! Stay!" It makes it impossible to fast-travel anywhere in the wild without that horse by your side. And horses are so not stealthy. Only way to get rid of a horse is to kill it.

Now to the actual bugs:

Should you decide and manage to take the horse "Frost" as an additional prize in the respective quest, it will be your horse. You can then buy another horse at a stables. You now have two horses, which I don't think you should be able to do. Your new horse will be named "(Your character)'s Horse", Frost will always be Frost. Should you try to take your new horse while still owning a living Frost it will be considered a crime and guards will attack on sight. Your new horse will run away, Frost will attack your attacker. In my case, Frost killed a guard.

If you fast-travel while riding your new horse, you and it will arrive at the location, Frost will remain where it was. After fast-travelling to another stables with my new horse I was then attacked by the NPC I "persuaded" to give me Frost, the horse I was supposed to steal from him. Yet, I could not kill him. After taking his HP all the way down he's just downed ("Revive me!"), gets up again after a while with full health and attacks again. And again. Very annoying.

Finally, I had to kill Frost because there was just no way to go somewhere to scout and explore stealthily with him. It hurt. He was a very brave horse. Seriously, I had tears in my eyes.


Mask:

A small graphics glitch happens with one of the Dragon Priest Masks, Molokien, where your head is just gone under the hood. The whole head is just invisible. It looks kinda cool, and it happens quite frequently.


Followers:

In Rift Watchtower, Lydia Housecarl was not able to follow me out again, because instead of going down the stairs or out the entrance she just stopped. If I told her to go past a certain point down the stairs she would run up to the top and stand one floor above the spot I was sending her too. I had to shout her down the stairs, literally with Unrelenting Force. Then she didn't go past the entrance door and stayed inside no matter what and I had to shout once more.

Also, why is it I cannot marry her?