Most the good stuff was done early in the 21st century, it's kind of overdone now which is why there's so much crap imo.

Essentials:

BATS - Red in Tooth and Claw (Not so well known but fecking amazing!!!)

At the Drive-In - Relationship of Command

Converge - Jane Doe (Although that's metalcore as much as anything)

McLusky - Mclusky Do Dallas

Hopesfall - Satellite Years

HUM - Downward is Heavenward

Million Dead - A Song to Ruin

Hell is For Heroes - the Neon Handshake

Sucioperro - Random Acts of Intimacy

Also Cool:

Beloved - Failure On

Glassjaw - Worship & Tribute

Refused - The Shape of Punk to Come

In Case of Fire - Align the Planets

Brand New - The Devil & God are Raging Inside of Me (You'll probably have heard this )

Meet Me in St Louis - Variations on Swing

Rinoa - An Age Among Them

Anything by Yourcodenameis:Milo

Kong - Snake Magnet (Oceansize drummer and bassist/quite noise-rock as well apparently)

Pulled Apart by Horses - S/t

Bands that are apparently good but I've not heard:

Fugazi, Shellac, Gospel, Envy

Good but overrated:

Fightstar - Grand Unification

Hundred Reasons - Ideas Above Our Station

Blakfish - Champions

Enter Shikari - Take to the Skies

Avoid:

The Blackout, We are the Ocean, Funeral for a Friend, Bring Me the Horizon

That was long...