I've not done one yet but some will do a hop bomb IPA where you put all hop additions in at the 20 minute mark. You get enough bitterness from the 20 min boil if you are throwing a crapton of hops in there.
I just tapped a keg of 20 minute IPA. 5 ounces of simcoe, 2 ounces of crystal and 2 ounces of centennial were added continuously starting with 20 minutes left in the boil. The hop flavor is ridiculous... astronomical... any number of adjectives. It's like drinking a glass of floral, fruity hop nectar.
I wouldn't normally use 9 ounces in the kettle but the hops were left over from dry hopping 10 gallons of Maharaja clone, so I figured why waste 'em.
I did an IPA with FWH, 30 minute, and late additions that turned out nicely. No hopback, since I use an immersion chiller. I dry hopped and oaked it too, and it turned out delicious. In fact, the keg's nearly dead.
Incidentally, it was a fairly offbeat hop schedule: Lots of Sorachi Ace, including an addition of Sorachi at flameout. It did not turn out to be lemon pledge, just citrusy and hoppy.