Let's see...I'm a Death Knight. Therefore I lack originality.
But let's compare
Vs Warlock- Lichborne+anti magic shield+ CC pet= Deathknight wins
Vs Mage- Anti-Magic shield for long for any magic shot, Anti-magic Zone.= Skill frost mage could get away
Vs Warrior-Takes a while but go vampire and it's easy.
Vs Priest- Silence while healing, kill before silence is off.
Vs Pally- Tough shot.
Vs Shammy- If the shammy has skill, he can beat you. However, it's a 35% chance of losing.
Vs Rogue- A skilled and geared rogue can beat you. A poorly skilled and low-geared rogue is just a bug on the wind-shield.
Vs Hunter- I find it funny. They have the materials to kick the crap outta of us. They're the one I hear complain the most.
Vs Druid- meh, didn't not kill enough druids. I can't give a good idea.
The worst thing is most of these class could beat us. I meet a lot of crappy Death Knights.. For once, I wish it was the bad people who would give a bad reputation.