I like effective characters, of any race, class, creed, etc. It must synergize and it must be effective at what it does, at minimum. That doesn't necessarily mean the most powerful, unless power was what was needed.

Once that's established, the sky's the limit. I just don't like for character I play to fail unless it's dramatic or due to pure situational challenge.

The characters I tend to hate are outliers, or character classes/races deliberately designed to be ineffective, like 3.5 Monks/Soulknives, or Samurai. It sucks the joy out of the game when I'm absolutely unhelpful and helpless.