Don't have one but I like this:
"If you don't love yourself, you can't love nobody
If you don't know yourself, then you nobody"
Chuck D http://www.youtube.com/watch?v=qokUi_c7a3I
It sounds better spoken and is mad poetic.
Also, a more 'conventional' one:
"Strategy without tactics is the slowest route to victory. Tactics without strategy is the noise before defeat."
Wrongly attributed to Sun Tzu.
“The thing I hate the most about advertising is that it attracts all the bright, creative and ambitious young people, leaving us mainly with the slow and self-obsessed to become our artists.. Modern art is a disaster area. Never in the field of human history has so much been used by so many to say so little.” - Banksy
Maybe not my favourite quote ever, but today I like it
I don't really have an all-time favourite, but I'll pick a few that stand out in my mind
"Falling is like flying just with a more permanent destination" - Jim Moriarty, Sherlock.
"I may be on the side of the angels, but don't think for one second that I am one of them" - Sherlock.
"If I started to do something that displeased you and you threatened me with failure, I was so much in awe of your opinion that failure, perhaps even if only much later, was inevitable. I lost confidence in doing anything for myself. I was unsettled, full of doubts. The older I got, the more evidence you could hold against me as proof of my uselessness; in some sense, gradually, you actually came to be right in the end." - Franz Kafka, Letter to his Father.