The United States of America as Religious Industrious with a special cavalry or rifleman unit. (Still might not be all that great tho.)
Phoenicia with a special scout ship that moves 4, expansionist/commercial. (Or whatever attributes get you to mapmaking fastest.)
All I can think of at the moment. Can't say I've really missed any of these but I have wanted to have a reason to play the Americans and I've been too lazy to try to mess with them in the editor. Plus I'm sure making a UU is beyond my ability.
I've always had a special liking for the Celts, probably due to my heritage. They should probably be Religious/Militaristic. For a UU ghe best I can think of is a raider-type based off a horseman, 3/1/2, to reflect the tribal cattle raids common in those days. It's not like you can fit bards and druids into the Civ3 combat system, nor would you want to.
When I palyed them I always changed their leader's name to Cuchullain (no offense to our noble and beloved moddie ).
Phoenicians are another good one, commercial/expansionist sums them up pretty well, and a galley UU with added movement would fit them well, except that it would be hard to get a GA that way.
Edit: I just realized that I would have made the Celts too much like the Iroquois. The UU idea was a lame one anyway. There has to be something better. Maybe a berserker type or something.
Unfortunately Im not even close to good enought with computers to make a new civ like the dane civ i saw posted.
I was thinking of great leader names. how about Brian Boru, Cuchullain (somebody mentioned him before), and Vercingetorix.
To keep up with the politically correct must have women leaders kick use Boadicea as the civ leader.
The UU is the hard part for me. Like Salvor I was trying to come up with a way to fit druids into the game. Im sick of all the UU being ancient or medievil. The problem is you cant really extrapolate a modern UU for a civ that died out centuries ago.
Which brings about a good idea - Why the hell do we want these unique units, in modern ages everyone is f..king unique!!! How about keeping those unique units at least untill the Advent of Firearms and Gunpowder??
Problem would be with such modern Civ as Americans, they never existed before invention of Firearms?