Charming: This is another fun power that is terrifying to developers. "Wait, so players can just CHARM the guards into helping the players kill the boss? That's an exploit, not a feature!" It just sets balance on its ear, making your pretty spreadsheet infinitely more complex. But it's fun!

EQ2's Coercer class can charm creatures and use them as pets. This is incredibly satisfying: you can charm a gnoll guard into attacking other nearby guards, killing two birds with one stone. Or if you're feeling cruel, you can charm a baby spider into attacking its mother, so that momma has to kill its own offspring. (Coercers are an Evil class, after all!)

But it seems EQ2's designers couldn't stand how powerful this was (especially in a raid situation), so they've nerfed Coercers again and again. These days, Coercers have a hard time maintaining a charmed pet, and it's not as much fun to play anymore. Too bad! Making this verb into a fun, yet balanced, mechanic is very tricky. (Though for the record, I think EQ2 is erring on the side of weak instead of fun.)

Taming is a controlled version of Charming. You can use this to bypass a monster (in the right circumstances), but usually the monster loses most of its powers once it's tamed. Plus, there are always limitations on the creatures that can be tamed. Nevertheless, taming is a fun part of WoW, DAoC, and UO.

What are your game's fun verbs going to be?

NEW VERBS are where it's at. The game's setting is much less important to me than what I get to do. I could easily enjoy another 20 fantasy MMO's, as long as they all have fresh exciting new things for me to do! This is where designers' creativity is really put to the test, can you invent a bunch of fun new gameplay options, and then reign them in so that they aren't overpowered, but are still tons of fun?

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Some other fun verbs to think about:

Transforming into a beast or monster (like AC2's Alchemist or WoW's Druid)

Controlling hordes of pets at once (like City of Villains' Mastermind or AC2's Elementalist)

Growing 50 feet tall and becoming kick-ass as a result (instead of it just being a visual effect)
Controlling the in-game weather

Being able to create dopplegangers of yourself (like EQ2's Illusionist)

Transportation powers like teleportation and portal summoning

Causing earthquakes on the terrain

Imprisoning your foes in alternate dimensions (like AC2's Oubliette... interesting in PvP)

Controlling nearby water to create tidal waves on command

Creating long-range turrets that can decimate foes at distance (like AC2's Tactician)

Powers that change with the season or time of day (becoming more powerful at night)

Innovative movement powers, like skiing downhill, leaping tall buildings, super-speed, or drilling through the ground (City of Heroes has many of these)

You can't slip these sorts of verbs into your game at the last minute. You have to plan them ahead of time. So pick as many fun verbs for your game as possible. This is the designer's chance to really shine. Worry less about balance and more about being amazing. Just be amazing! Almost everything else will be forgiven if you're amazing.