Lions are really cool but lack in personality (not to mention they are venomous). Puffers are really cool and have great personality, but are a huge bio-load. You might get away with another trigger, but I wouldnt recommend it. Boxfish would work, maybe an eel or grouper.
Remember that aggresive tank can be more work because they are meat eaters and poop alot, meaning frequent water changes. You will be limited on inverts you can have because your fish might eat them.
heres a link with some descriptions http://animal-world.com/encyclo/marine/salt.htm