Let's see....

The pseudospecial characters are:

Lini - Moogle Knight - Knows Mog Guard and Ultima Charge - You need to use The Hero Gaol on a mission

Pallanza - Gladiator - Knows Blitz and Ultima Sword - You need to use.....Wyrmstone, I believe.

Cheney - human Hunter - Knows Capture and Ultima Shot - You need to use Snake Shield.

There's also someone you get by using Elda's Cup, but I missed that one.

And you can get two for simply completing missions. One is a Sage, the other a Sniper. I know you are able to get the Sniper by winning that clan league final battle thing, but I'm not sure about the Sage.

....It'd be a big spoiler to list the unique characters, though.....and I've no idea how to work the spoiler tags. =P