most larger fish, for the most part, are agressive, so you could try a bunch of smaller fish, like clownfish, they're pretty open swimmers, and great to watch. I also have a black & white heniochus (butterfly/bannerfish family). She's the most interesting thing i have in my tank. She never hides, ever, and always swims right by my face when i'm near the tank, as if to show off for food. you could try a wrasse, but i'm not sure how agressive they are, as there are a LOT of different wrasses. I have a fairy wrasse, and they only get about 5 in. or so. He's not agressive at all, and is kinda skiddish, but i just put him in a week ago, so he's supposed to open up more. You could try some sort of jawfish, or goby, like the yellow watchman goby, although they like to hide in the caves, you can always see their little heads poking out... Also, firefish are amazingly beautiful, and they like to be in groups, so you could get a few, and they'll flock together. They're also small, but they like to be in the open (from what i understand, but i could be wrong), and they're not agressive in the least bit. Just my $0.02, hope this helps!!!
I'm not sure about larger fish, though, as i only have a 55 gallon. When i do get a large tank, it's definately going to be agressive (sharks & rays).
Jenn
BTW, all of the above are really easy to care for.