I'm sure this has been done before, but I started a pure thief character and it is tons of fun. My rules for roleplaying this character are listed below:

• Steal EVERYTHING I use (equipment, weapons, food, etc), never purchase anything
  
• No spells, no enchanting
  
• Only have character active in cities or towns (except for Thieves Guild Questline)
  
• No quests (except Thieves Guild)
  
• Alchemy/smithing with stolen items only
  
• No weapon use (I carry a dagger just because it looks good)
  
• Do not kill anything (difficult sometimes, but patience with sneaking can work around this)

Please let me know if you have any more fun rules to add for this build. I highly recommend it and I levelled up faster than I thought I would (10 levels in the first hour). Basically, after escaping Helgen, I discarded all of my equipment so I would be forced to steal everything I would need. It was chilly for awhile but thankfully I found a gullible hunter to steal from on my way to Riverwood. I am playing as an Imperial Female, but obviously any race could be used.

*playing on console

Well, this is slightly off topic, but I love not killing anything in the MGS games, granted, I play with one extra rule: I cannot disturb anyone either, meaning I can't even use my tranquilizer dart, non lethal sniper rifle, or knocking them unconscious from behind unless I absolutely see no way forward "(rules apply to robots as well as humans, but if I do have to kill a robot, it has the added advantage that I can use whatever I want). It makes the game really really hard and I have to be patient.

however, in skyrim that would be hard, considering the game forces you to kill in many quests. If you want to play a pure thief, go play Oblivion's theives guild, in there, you would have to pay 1000 gold fine if you killed anyone

Seems pretty awesome! Though I couldn't abide by the no killing rule.

Sounds like fun up to the no killing part. Why would you steal weapons if you aren't going to kill? Maybe to sell them? And I guess you aren't planning on looting any dungeons if you aren't killing.

So basically you are doing Theives Guild and...what? Robbing houses?

I think it could be interesting, but without killing, it really limits you IMO.

The no killing rule is definitely the hardest to follow, and it might be unavoidable at some point (end of the Thieves Guild quests), but since my thief is only active in cities and towns I can sneak around people in my way. If I was dungeon-diving or doing other quests then this would be more difficult.

I will do all of the Thieves Guild quests when I join, but for now I am just breaking into people's houses and pickpocketing. I stole a dagger purely because it looks good strapped to my side, and I will steal a crossbow when I come across one for the same reason. It takes awhile to get used to the play style, but a fun and different way to play the game.

Does your third rule mean you never go into any dungeons?

Also, what difficulty do you play on?

The only time I will go into dungeons (or anything outside of a city or town) will be if it is required for a Thieves Guild quest. Currently I have the game set at the default difficulty but playing on Master shouldn't be too bad since I am not involved in combat.

I tried this and failed. My main rule was to only use the Thief skill perks and no other. Joined the thieves guild.

Way too many times melee combat will happen and can not be sneaked around. When that happens your super weak weapon skills get you killed. Poison helps, but poisoning a blade before every swing gets old and potions do run out, unlike skill and upgrades and enchantment which don't.

Maybe if you could start the game at 50th level so your sneaking skills and such are about maxed, but low level was impossible and I had to give her up.

But you do beat people up, dont you?

Staying within the cities and towns has been an easy way to avoid MOST combat situations. The only time (so far) that I really had to work to avoid getting into combat was when sneaking through the Ratway the first time around. Here patience paid off and I was able to get past the few low lifes planted down there.

Yes, I believe the intro quest for the Thieves Guild has you rough up a few people in Riften...but beating people up for the Thieves Guild doesn't break my rules. Also, I will have to kill to complete the Thieves Guild Questline, but that should be the only time my blade will taste blood.

Are you saying you sneaked past those two? Love to know how you did that. Inviso potion or did you already have a 80+ in Sneak?

If he doesn't kill anything, does it really matter?

Lol it was a pain but I managed it. My sneak was around 40 and I waited until the smaller guy walked towards the entrance to investigate. There are two small alcoves you can hide in as he walks past, then you move up towards the bend in the tunnel where they are initially talking. If the timing is right then the bigger guy is standing with his back to you by the fire and you can sneak past. It took me a few tries to get the timing down but it's very dark down there so that helped alot.

Same with my pure thief except I kill in extreme cases(my back is too the wall) I prefer spells and running if I'm discovered and if that doesn't work I use my stock of paralysis poisons (I have 62 right now 4-13 seconds). It's pretty fun and right now I have a steady supply of gold and Honeyside is stocked full of gems, armor pieces, weapons,and various items of personal value(I have five bugs in jars! working on locating the sixth)

I like the idea of stockpiling a few paralysis potions to aid in an escape if i get cornered. I might not kill anything while playing, but I might need to slash one with poison so I can escape.

it comes in handy.