Tenrou Star - Hix
Hix is another average short-range fighter with decent but not outstanding stats (other than his high Luck). You certainly won't lament having to use him for some story scenes, but you probably won't use him much after.
Tensui Star - Tengaar
Essentially a long-ranged mage; she has high enough Magic and MP to stand with the best of them, and her physical capabilities, while nothing great, aren't terrible either. Gets some pretty good equipment choices to offset her low HP, too. Give her a good rune and let her get to work.
Tensyo Star - Clive
One of the better long-ranged attackers, having very high attack for one as well as solid Speed and an incredible Skill stat. His lack of magic ability hampers his usefulness in the late game, though.
Chikai Star - Leon
Mathiu's brother doubles the effectiveness of your Charge attacks in war battles, but doesn't do any fighting himself.
Teni Star - Pesmerga
Another all-or-nothing fighter type, boasting extremely high HP, Power and Defense (as well as great armor choices), but abysmal Skill, Magic and Luck, which means he'll miss a lot and isn't good with magic. He's certainly one of the coolest-looking characters, but not one of the most useful.
Chikou Star - Fuma
A Ninja, which makes him handy in war battles, but in a smaller fight he's only okay. Another mostly forgettable ranged fighter with high speed and decent attack.
Tenku Star - Kreutz
Basically a slightly weaker Humphrey, only trumping him in having a higher base Defense. Not a bad alternative, but at the same time, there's not much point in using him when you've probably invested more time and money in other, better front-line fighters.
Chii Star - Milia
A mid-ranged fighter with power and defense comparable to most front-rangers, as well as surprisingly high speed. Her magic power is lousy, but not a bad choice on the whole.
Chikyou Star - Joshua
Joshua rounds out the Dragon Knights war unit, which allows you to cast a powerful magic attack. Useful in the right situations, but he doesn't fight otherwise.
Chibi Star - Futch
High speed and luck, but relatively average, midrange-fighter-oriented stats otherwise. Just like a bunch of others in Suikoden. Ho hum.