I remember finding a field of high-level Leprechauns in Dark Age of Camelot and started kicking their behinds just for the fun of it. They had great sounds, animation and spewed insults about my mother.

For whatever reason, they were just a perfect level to make it a great deal of danger and yet a lot of fun. When one of them dropped a great weapon for me I was sold. I spent WEEKS killing those little creatures (and dying quite a bit due to their habit of respawning in a horrible pincer movement) and loved every second of it.

It was just a GREAT mix of danger, combat, comedy and loot.

What I define as a "grind" is when a mob is not interesting, no danger and just NEEDS to be endlessly slaughtered to reach a game goal. That is what got me to quit WoW.