180 gallon as a bar? Definately African cichlids from malawi (mbuna, haps, peacocks, take your pick or a mix of them). A frontosa tank would be nice too, although those guys are pretty sedate. Or a planted discus tank if you want to go all out....mmm...that would be nice.
A more "monsterish" approach would be an arrowana or some stringrays perhaps.
What about a gar? Maybe some rays? A good variety of large cichlids. They can defiantly give a good wow factor at feeding time. I know you say no to cichlids but they do look great in a 180.