Least player class in WOTLK

[Elipas]

Play some enhancement shaman and assassination rogue and of course a paladin (jk)

[Disktrasa]

Rarity - Difficulty - DMG.

Feral Cat - Hardest class in game to play - Can pull really good dmg. (top 5)
Combat Rogue - Challange but still not too hard to play - THE nr 1 best dmg class on single target.
Enhancement Shaman - Imo 2nd hardest class in game to play - low dmg.
Moonkin - Rather easy to play - Bugged recently - Bad damage (Should be able to do good dmg)

Even tough some classes are more unplayed then others I still found myself in 25 man raids where I se 4 Feral cats and 1 Paladin / Hunter / DK

If I was you though I'd rather try a class that's fun, Like Shadow priest, There aren't too many of them and they bring really good buffs to the raid, specially a raid with low geared people who lacks hit (most casuals don't bother getting hit cap)

[kawasakigpz]

Warlock is least played.

[mystiquue]

Why not try a druid as you pretty much have a bit of everything there all in one char!
by the time you get high levels you'll have dipped into every pool and can decide what you like best to make as a second char.