Has anyone found Labyrinthian in the game? because I haven't.
Yes, I have. It's not that hard to find, you should look
Didn't go in yet 'though, because I think there's some quest related to it.
About random encounters and easter eggs, I've seen quite a few:
- headless horseman (three times by now)
- tree stump with a fallen cup and ants marching on it (presumably attracted by the contents of the cup)
- ye typical three Imperial/Stormcloak/Thalmor soldiers with a prisoner (once, three Imperial soldiers with a Stormcloak prisoner marched right into Winterhold >_< Real smart)
- ye typical noble guys travelling the roads with a guard
- Khajiit caravans, either at a city or running/walking along the roads
- normal courier, or Stormcloak courier (once, a Stormcloak courier ran past Whiterun, heh)
- ice mage fighting against fire mage (seen it twice by now, the first time a stupid assassin suddenly attacked me while I was watching)
- after doing Sheogorath's quest (with a few references to The Oblivion and Shivering Isles' MQs), I met a woman along the road who constantly said "Wabbajac, Wabbajac, Wabbajac". Didn't really know what to do with her. (didn't carry it either in my inventory, sadly)
- Highwayman who demands for money and valuables (multiple times)
- Highwayman who turned out to be an alchemist?

His body still lays on the road where I killed him.
- Fugitive woman who asks for directions to the nearest town, and gives me the location of some bandits
- Mercenary going to stop "some trouble" somewhere nearby. I asked once to help her, but my persuasion wasn't high enough. Still didn't do it yet.
- Vigilants of Stendarr fighting against some skeletons multiple times. Vigilants always won.
- Vigilants of Stendarr fighting against a group of high-level vampires near their nest. Vampires won. Then I got my ass kicked a few times before I decided to blast off while healing continually.

- Farmer with a painted cow going to "appease" giants nearby. By all means, follow him if you never did!

- On that note, I've also seen a giant walking closely behind a painted cow ...
- A guy running up to me, giving something and threatening me to not tell anything about it. Ran off again, and from that same direction (they ran next to each other at a certain time) someone else came running up to me, asking whether I had seen this guy. Seeing how the other one dared to threaten me, and gave me something I couldn't use at all besides as a burden, I immediately ratted him out. the it was like "Ha! Found you!", The first guy chickening out (he didn't seem to even carry a weapon with him?) and being made into a sifter by the other guy's arrows. me and a guard ("This should be fun!") stood there and watched it. ^^
- Fake imperial guards (also multiple times). Damn hard, these opponents.
- a toll bridge, manned by bandits. Well, not really a bridge, but heh, they still asked for money. I didn't like the principle, so I went back a bit and looked for another way to get there. Wanted to finish a quest first before taking them on, I was already carrying too much loot with me.
- A carriage clearly attacked by Falmer
- an abandoned camp of adventurers who left some kind of journal, stating they wanted to put a stop to all those attacks on the road (probably kinda related to the carriage)
- a random fort I walked in, where I met a scared adventurer fighting off a "special" spider, who remarked the whole fort was filled with them before running away like the wind.
- a lighthouse with a gruesome scene and a nice sidequest. I felt with the inhabitants 'though.
- and I'm going to stop here

- ah, and maybe also some bugs, like a sudden dead Hargraven falling on the ground before me, a noble guy on his horse floating in the air going up and down fast before disappearing in the distance (came galloping down the road again a few secs later), mammoths falling from the sky, ...
/edit: which makes me remember, concerning mammoths, I've also discovered a frozen mammoth in Ice. Also an easter egg.