Feral/fury/wolf druid, or wolfbarb. The druid is damn strong, can go apeshit in hell even in hardcore, against strong mobs, with semi-decked out gear. Also kicks good against bosses. Leeches damn good .. the damage is good, but not super-over the top. But will crunch through most mobs, maybe struggle a bit against the strongest. Then you would need super-decked out gear. But finding that one early in a hardcore ladder season, means you can build the entire season around it. Nightmare is a blast, just punch through anything, bosses goes down quick as hell. And the fast running, is almost like teleporting. Build feral rage to the largest level, then switch to fury.
Truly a fun build, 8/10 on my scale. Only surpassed by freezing arrow zon, bowa, 200% fcr nova sorc and maybe some few other builds. It's up there.
D2