Well hello there!
Recently, I've been playing Olaf quite a bit. I played him jungle only at first, taking his Q skill first, Undertow. Deciding to experiment with him a bit, I went solo top and maxed Undertow before anything else. This actually worked quite well.

Olaf's main disadvantage in the solo top lane is his lack of range - any opposing ranged champ who knows what they're doing isn't going to let you walk up and smack them with 340 true damage. This skill sequence allows for a great ranged harass and chasing mechanism, while still obtaining your E early enough for it to do massive damage.

PROS
Great Q harass by rank 3
Nearly impossible to gank
Excellent zoning capability
Brilliant chaser, very difficult to escape from
High dueling capacity, sometimes even against multiple opponents
Brolaf skin gives 28% extra imaginary coolness damage

CONS
Can get mana hungry
Long CD without picking up the axe
Worthless if you can't hit with your axe
Not ideal against leap champions such as Jax or Talon

An Olaf who maxes his Undertow before all else is an incredibly rare sight to see. Nearly all those who play him will max his Reckless Swing first for its massive early game damage. However, any opposing top laner with any sort of kite mechanism can easily give Olaf a hard time while chasing them around.
Most Top Laners wont be expecting the damage output from your Q, and will focus mainly on staying away from your E. Because of this, most will be a fairly easy target for you to harass.