has anyone ever rapped in iambic pentameter?
It could be argued that a lot of rap is done in Iambic Pentameter. Eminem has a few songs that have verses in it. I believe 'The Kids' is one of them and as the below teacher noted in trying to get his kids to see the value in studying Shakespeare, the first verse of I am is allegedly in IP. Now I haven't bothered to prove it so take it with a grain of salt. Probably best if you listened to it so you can hear when he puts stress on the words.
http://mscronksclass.weebly.com/1/post/2011/11/eminem-ic-pentameter.html
His PALMS are SWEATy, KNEES weak, ARMS are HEAVy
There's VOmit ON his SWEATer alREADy, mom's spaGHETTi
He's NERVous, but ON the SURFace he LOOKS calm and READy
To DROP BOMBS, but HE keeps ON forGETtin
What HE wrote DOWN, the WHOLE crowd GOES so LOUD
He OPens his MOUTH, BUT the WORDS won't come OUT
He's CHOKin, how EVeryBODy's JOKin NOW
The CLOCK'S run OUT, TIME'S up OVer, BLOah!