HAIDUR!
*Please notice that this build is still incomplete, I still need to change around few things (Don't have LoL installed in this computer) I'll complete the build when I have a chance to access to my main computer*

This is actually my first guide/build on Mobafire, please notice that this build has tons flaws, but this worked for me in my Olaf games, I think Olaf has the highest winning rate for me because of his late game ability. This build might seem ghetto to you, but if you played this champion correctly with this build you're pretty much unstoppable.

This is really a very unique play style of Olaf, and it's very unstable early game, but if you can make it to late game there should be no problem.

Greater Mark of Desolation
-I don't really need to explain this, ArP for some damage.

Greater Seal of Vitality
-I like to take HP/18 for most of the squishy champions, the way I build Olaf makes him no where near "tanky" I would need that extra 175 HP at 18, sometimes just that tiny bit of HP makes him stay alive.

Greater Glyph of Shielding
-Some extra MR throughout the whole game.

Greater Quintessence of Fortitude
-I really like these quints, I use this for almost all my builds, that extra 78 HP REALLY makes a difference, I dunno how many times I got away with like 10-20 HP.

I took improved exhaust and ghost, don't need that 15% magic penetration since Olaf don't have any sort of magic damage, I went pretty much full offense.

I'm pretty sure I'm the only one who builds Olaf squishy, again this might be "weird" "ghetto" "OH IF THEY ALL FOCUS YOU YOU'RE NOTHING". Please let me explain down at the "Gameplay" section.

I max Q (Undertow) first, followed by W (Vicious Strike), taking R (Ragnarok) whenever I can, and max E (Reckless Swing) last.

Again this seems REALLY ghetto, but it works for me tons of times.

The Q deals great damage, with ArP seals and the passive (if you pick up the axe it lowers the CD) you can constantly spam this skill to harass in the laning phase, if me and my lane mate is doing good and the enemy team doesn't have a very strong Lv1, I usually can pick up firstblood while they running toward to their towers.

I choose to max W next because of the life-steal, this is why I didn't take any sort of life-steal items early game, with the HP quints and HP seals, you can get a decent amount of damage from this skill.

E is a very good skill early game, it deals great damage to the enemy, but in return, it deals damage to yourself, this is why I didn't take this skill early. (I might want to leave W at Lv3 just for a decent life-steal and max this as my 2nd skill)

R is what make DPS Olaf viable, during the ulti, Olaf is a unstoppable beast. However, there are exceptions which kills Olaf, such as exhaust, ignite, teemo's blind, etc. I will explain how to "counter" these situations in the "Gameplay" section.

I took exhaust to buy Olaf sometime to do the life-steal, while fighting other carries 1v1, it really turns the situation.

I feel ghost benefits the most for Olaf, to keep up with other champion who is faster than Olaf, combined with his ultimate, he can chase up to pretty much anyone.

Pros:
-Very high damage output
-Great chaser
-Rarely lose 1v1

Cons:
-Semi-Squishy early to mid game, ends up with 3.2k+ HP but no Armor/MR, which still considered squishy
-Ignite really kills him

First of all, if you're playing Olaf as a tanky-dps in your past experience please throw all that thinking away, the way I built him makes him a truly "berserker", the more you fight the higher chance you stay alive.

You have to farm A LOT due to the cost of this build, you'll have to farm non-stop, if there's no minion then take the jungle, take the wraith, take the mini golems, TAKE EVERYTHING WHENEVER YOU CAN. The keyword to DPS Olaf is farm.

*You'll need some good positioning/skill shots in order to use this build successfully, otherwise it's just a suicidal build*

Early game
-Take boots of speed, 2 hp pots, 1 mp pots, boots for that extra speed you need to run away/chase at lv 1 fight, kite the enemy with undertow, watch the mana though, you don't want use your mana too quick.
-I prefer duo lane bot, solo top if there are no better solos than you. Solo mid if no one is going mid and your team is trolling you.
-(All the explanations is going to focus on the duo lane) Because of your Q (Undertow) you can harass pretty decently if you hit the enemy, make sure not to push the lane too much to avoid ganks, take last hits in the safe range (Means if the enemy team have no will of harassing you while you take the creep) Keep harassing, keep last hitting, stay safe. Now if the enemy team is being pansy/playing defensive due to your Q and your laning mate's poke, now if you have a chance to initiate the enemy team... Actually let me take that back, Olaf really need his lane partners support to get some early game kills, if you're laning with a support or someone who really doesn't do anything or does not have any hard CC then just stay safe and farm, you might wanna try look for a gank with your jungler if possible. Anyway you'll need your lane partners help in order to get some success early game kills. A fed early game Olaf with this build is deadly.


Mid Game
-Pretty much same as early game, you just keep farm your *** up, you'll deal TONS of damage after IE and PD, if you can farm those 2 core items before 25 it's pretty much game.
-At this stage you just keep farming the empty lane, farming the jungle, LOOKS for ganks, make sure you join the fight last, NEVER start a fight unless you're sure it's a 1v1.

Late game
-Now it's the time where Crit Olaf really shines, I'll have to explain everything in detail in the team fights.
-Again, never initiate a fight, don't get caught, if you did get caught, just pop your ultimate and your ghost and run to your base, NO ONE CAN'T STOP YOU FROM ESCAPING IF THOSE TWO SKILLS ARE UP. (Well, Jarvan might trap you...)
-Join the fight last, target their main damage output first of course, if you cannot reach their main DPS, then target their hard CC (usually casters such as Veigar) there should be NO WAY they can stop you from reaching their caster since they're chasing your teammates/you cannot be stopped with your ultimate. It usually takes no more than 4 crits to take a squishy (around 2.5k hp with less than 150 armour) caster/AD dps. Some stuff can't really be explained by text, you need to have the feel of when to join the fight, which requires experiences of playing.
-At this point you should be unstoppable, the only thing that will kill you is the exhausts and ignites, you can probably take 2 or 3 enemy champions by yourself if they have their spells down, the only way to counter this is to wait until the exhaust/ignite goes off then join the fight, (ragnarok ignores exhaust's slow) just pop your ultimate and ghost if they're focusing you and using ignite/exhaust on you. Kite them around, the only one who can chase up to you is probably the AD DPSes they got, wait for the ignite/exhaust to go off then fight them. Dominating in late game does NOT make you invincible, it's just make you a heavy damage dealer that don't seems to die due to the life-stealing.

This is a very unique build for Olaf, please try it out before leaving a rate, I've played many games with this build, rarely fails if you can make it to late-game. Please leave a comment for anything you want to say (Concerns/Suggestions/Etc)