Bwl an Naxx.

Bwl - blackrock rules, cool endboss, overall more tasks for most classes during the raid especially compared to MC. And I like the design with fighting through different stages till endboss on top.

Naxx felt also nice to fight against humanoids & undeads and cool bossfights too. And ofc it felt a little superior to be in a naxx raiding guild xD but not this time (for me)

My favorite raid is Redridge!

I voted BWL but ZG was definitely a close second for me. They both represented a big step up in design from MC and Onyxia before them and enjoyed doing them more. To be fair I did not do AQ much or Naxxramas at all for comparison so my options are more limited.