My previous favorite rap lyrics came from Tupac:

All respect to those who break their neck to keep their hoes in check
Cause oh they sweat a brother majorly
And I don't know why, your girl keeps paging me
She tell me that she needs me, cries when she leaves me
And every time she sees me, she squeeze me, lady take it easy!
Hate to sound sleazy, but tease me, I don't want it if it's that easy

They have recently been eclipsed by this stanza from Eminem:

Where the fuck is Kanye when you need him?
Snatch the mic from him, bitch I’mma let you finish in a minute
Yeah the rap is tight
But I’m tryna spit the greatest verse of all time
So you might want to go back to the lab tonight and um
Scribble out them rhymes you were going to spit
And start over from scratch and write new ones
But I’m afraid that it ain’t gonna make no difference
When I rip this stage and tear it in half tonight