While there are a ton of AYCE sushi spots in Vegas, Sushi 21 is by far one of my favorites. They've got a pretty hefty menu of AYCE selections, so you aren't faced with too much repetition if you want to switch things up, and if you get bored with the menu, the chefs always have a little special item they can throw together for you.
My favorite specialty has seared salmon with kiwi - one of Kenny's awesome little creations. Just the thought of this delectable little dish makes me want to hop in the car and head over for an early dinner.
Meanwhile, if you're going to stick to the menu, I would suggest the popcorn lobster roll - somehow the sweet of the eel sauce and spicy mayo mix with the coolness of the California roll and the heat of the deep fried lobster bites to form the perfect symphony of greatness. Seriously. Try it.
Throw in a two for one deal on hot sake and you've got a pretty freakin amazing meal!