Assuming we're talking about melee dps, then dw frost DK. I just like them.
If you want the broader "people in melee range" (i.e. including tanks) then Paladin (love prot, but I can't stand ret). Tankadin is my main & always will be, I wish Bliz would piss off & quit trying to shove ret down my throat - there is only one true paladin spec.
If you want the melee dps class I'd be happy playing any spec of, then warrior (I don't like 2h frost & haven't played unholy in ages, whereas I like both fury & arms). I quite enjoy the "lilt" of the warrior prio, as it cycles through colossus smashes.
If you want the class I'd be most happy playing as a tank/melee-dps hybrid, then Monk (love brewmaster & windwalker is ok). Love the maneuverability, love throwing beer at people, like playing a ranged capable tank + a fairly spammy melee dps.
Rogue feels constantly energy starved to me.
Haven't played Feral in ages & they had the same issues as rogues for me last I tried. Enhance was fun last time I tried it, but healer+ranged caster just synergises too well for me to have re-geared my shaman as melee (especially given how unwanted melee tend to be).
And I've raided at least current tier flex with all of them except feral & enhance, so my familiarity is fairly up to date.