I made a 30th-level fighter - 2:20 minutes, which is fast for me. 30th-level Fighter
Basically, he comes charging out of the shadows, right into a wave of enemies, smashes everybody around him, dancing through the enemy forces like they aren't even there and when they finally take him down...He's back up to full health. And then he keeps on going, turning everybody around him into mincemeat...And when they finally wear him down and corner him again...
...He teleports back to his allies for healing.
This is awesome.
...Did I mention he has a Lifedrinker greatsword? +15 HP every time he kills a minion. Army-smasher, possibly literally.
Of course, like all optimized characters, he has a weakness - In his case, single, or only a few, enemies. In which case, he's merely effective.