Goes like this:
I'm so heartless, thoughtless, lawless and flawless
Smallest, regardless, largest in charge and
Born in New Orleans
Get kilt for Jordans
Skateboard I'm gnarly
Drake, Tunechi and Barbie
Why is this so delightful? My poetry terms are rusty, but I think the delight results from a complexly intertwining rhyme scheme with assonance (which, as you may recall from a bygone English class, means repetition of vowel sounds.)
At line three the structure changes utterly, in mid-sentence (enjambment!), without any break in flow. The phrases shorten, the lines start to end-rhyme, the meter shifts. The first two lines are roughly trochaic tetrameter, so four sets of stressed/unstressed syllable pairs; the assonant 'ah's are stressed and the rhyming 'ess' endings are unstressed. Lines three through five are dactyl-trochee pairings: SKATEboard I'm is a dactyl (stressed-unstressed-unstressed) and GNARly is a trochee (stressed-unstressed).
In the final line he lets Drizzy and Nicki be the stressed syllables, leaving his own moniker humbly unstressed. Perhaps an acknowledgement of his semi-emeritus, godfatherly role in today's rap world?