My favorite type of singer would have to be the ones that sound the most unique, not necessarily the best singer. But, I think you don't have to have a great voice to be a great singer...just something different.
I made a short list of my favorite singers and why I like them. All of the singers are rock/alternative singers because that's all I ever listen to! Must expand my musical taste...
Steven Tyler of Aerosmith

Oh how I love Steven Tyler! He has a perfect voice for good old rock n' roll. To me, his voice is raspy and husky, yet smooth n' flowing. Also pretty clear...I can almost understand everything he sings in a song. I also enjoy his style and personalty...he sure has a lot of spunk!
-Best Songs-
Walk This Way
Dude (Looks Like a Lady)
Dream On
Love in an Elevator
Janie's Got a Gun
Chad Kroeger of Nickelback

I just love how you can hear emotion in Chad Kroeger's voice. To tell you the truth, I would not even probably listen to Nickelback if it wasn't for him. I've seen Nickelback live in concert and Chad Kroeger sounds just as good live as he does on the radio.
-Best Songs-
Never Again
Figured You Out
Too Bad
Something in Your Mouth
Animals
Side of a Bullet
Someone That You're With
Shakin' Hands
Vince Neil of Mötley Crüe

Vince Neil may not have the best voice in rock n'roll, but he does have one of the most unique. I absolutely love the whiny and high-pitch sounds in his voice. In Mötley Crüe's book, The Dirt, Vince said his voice sounds like "Rob Zander with his balls pinched." Interesting way of describing your own voice, but, it seems to hit the nail on the head.
-Best Songs-
Dr. Feelgood
Dancing on Glass
Shout at the Devil
Kickstart My Heart
Sticky Sweet
Rattlesnake Shake
Rock n' Roll Junkie
James Michael of Sixx: A.M.

James Michael's voice sort of reminds me a lot of Chad Kroeger's. Like Chad Kroeger, he really knows how to put emotion in his voice. It's mainly sadness in The Heroin Diaries Soundtrack, but I'm sure he could make his voice sound anyway. On top of it all that, he has an incredibly powerful voice.
-Best Songs-
Life if Beautiful
Heart Failure
Girl With Golden Eyes
Van Nuys
Pray For Me
Austin Winkler of Hinder

Gravelly, raspy, and rough...that's the best way to describe Austin Winkler's voice. I first fell in love with his voice (and Hinder) back when I first heard Lips of an Angel on the radio a few years back. Hinder is another band I witnessed live in concert. He still impressed me!
-Best Songs-
Lips of an Angel
Get Stoned
Room 21
Better Than Me
Take it to the Limit
So, there you have it. Of course, my list of singers doesn't end there.
But, before I seal this with a kiss, let me ask you something: who is your favorite singer?
Sealed with a kiss...
~Raven