Good topic. I don't think you can say there is ONE best ever. There have been a few classics already mentioned. Here are some others I would nominate:
Well, she was just seventeen -- you know what I mean.
In the time of chimpanzees, I was a monkey.
I was born in a crossfire hurricane.
Well, it's one for the money, two for the show, three to get ready, now go, cat, go!
Hello, Darkness, my old friend.
I've been a bad, bad girl.
I hurt myself today to see if I still feel.
I ain?t a killa, but don?t push me; Revenge is like the sweetest joy next to getting pussy.
Well, you can tell by the way I use my walk; I?m a woman?s man, no time to talk.
Just a small town girl, livin' in a lonely world.
So, so you think you can tell, heaven from hell, blue skies from pain.
Go, Shorty, it's your birthday.
Imagine there's no heaven.
I stand up next to a mountain; chop it down with the edge of my hand.
She was a fast machine, she kept her motor clean, she was the best damn woman I have ever seen.
If I leave here tomorrow, would you still remember me? <- DEFINITELY IN TOP FIVE IMO.
Leaves have fallen all around; time I was on my way.
I once had a girl or should I say, she once had me.