Here are three that come to mind:

The Girl - City and Colour
Heaven Bound and Glory Be - Kevin Devine
Medicine Man - The Hush Sound

I can sing along to:

1. Hot Hot Heat
2. Three Days Grace
3. The All American Rejects

Somehow I had completely misread this as songs instead of artists. For artists, it would be:

City and Colour
The Avett Brothers
Sufjan Stevens

The top 3 I usually sing along with:

Night Wish
Loreena McKennitt or Enya {depending on the song}
Blackmore's Night

Hmmm I would have to say Billy talent, Lonely Islands and...Eminem lol

Green Day
Metallica
Shinedown

I suppose the three I sing along to are as follows:

Superbus
Gackt
Celldweller

Amazing. . . 3 different languages, and I only speak one ^^;

linkin park
rise against
any celldweller remix

right now my top three would be:

1)selena gomez - pop singer / actresst.
2) garth brooks - country singer.
3)Trace atkins - country singer.

1. All This And Heaven Too - Florence and The Machine
2. Never Too Late - Three Days Grace
3. Meltdown - Rin Kagamine (VOCALOID)

top three bands i sing along with are:
AC/DC,
Garth Brooks,
and
Queen.

My top three would be
Shinedown
Linkin Park
and any Wrock band.

Adele
Owl City
Taylor Swift < - XD

Madonna
Owl City
Queen
Freedom Call
& Nightwish

One Direction
Night Wish
Alkira

The completley different styles of music but I love them all equally