I AM THE MESSENGER - Markus Zusak.
YEAR OF SECRET ASSIGNMENTS or FINDING CASSIE CRAZY - full disclosure: this is multi-POV, with three girl POVs and two (okay, three/four, but mainly two) male POVs. But it's lovely and you must read it.
AVOIDANCE by Michael Lowenthal. But heavy. Very heavy. And scary.
THE PERKS OF BEING A WALLFLOWER by Stephen Chbosky doesn't exactly have a 'strong' voice, in my opinion, but it does have a sweet and engrossing one.
WHAT HAPPENED TO CASS MCBRIDE? by Gail Giles is multi-POV with two male POVs and one female POV, but mostly 50/50 between a female and male POV. One of the strongest male POVs I've ever read, because since the female POV is 98% her talking to the main guy, it's...scary. But great.
And BREAK, obviously.
Onto the books I don't like as much, but I'm willing to concede their narrative voices:
DOING IT by Melvin Burgess.
MARTYN PIG, CANDY and ROAD OF THE DEAD by Kevin Brooks.