In all Ork Clans there are some elements I like, but my favourites are:
3.) Snakebites: I do love Orcs'n'Goblins in WHF, and I do love the savage nature of Snakebites. You also get to use lumbering Squigbeasts in a universe of spaceships and plasma cannons - what's not to like?
2.) Blood Axes: plans, inside of plans, inside of... Waaagh! I do like them for their cunning, as well as the fact that you can paint a tank in yellow and pink stripes and call it a "clevva camouflage". Being able to easily use IMperial units as "allies" is just an added bonus.
But, there can only be one...
1.) Deathskullz: loot all da fings! I have always been into building and converting models much more than painting or gaming. I also always think about "how can I convert this model, and what else can I do with this kit?" ... which is an approach Orks excel in. Deathskullz are the epitome of this attitude, so they naturally are my favourite clan. There is also a joke in German about the colour blue and being wasted, which is kind of not translatable, but is spot on for me as well.
Honourable mentions go to:
X.) Freebootas. Similar to Deathskullz, but with added pirates. Everthing gets better with pirates!