Get the Defender, it'll serve you well for a while, and at the moment it's probably the best fighter available. The Patriot is another good choice, it's more manevourable, and accellerates faster, but can't carry as much ordanance. I'd go with the Defender if I were you.

If it wasn't for the inky blackness of the night you wouldn't appreciate the brilliance of the stars...

I've been using the Crusador. You can load it out nicely and it makes a very good battle platform.

The Defender is a good choice at that point in time, if you can afford decent equipment. One of the best fighters is sold somewhere in the badlands but you cannot get it if you are on shooting terms with the criminals ... You may want to keep this in mind for your second run through the campaign.

The Starflier and the Patriot are better fighters than the Defender (I beat the game with both) but most people do not appreciate their values until long after their first time through the game, if ever.

@Shelog: I'm with you on the defender. A truly great ship that one. Since then I've owned the Cavalier, the Crusader, the Drgon, The Baracuda and just got the Anubis. Only the Anubis is as good IMO.
Whats the decent ship in the Badlands???

MegaKid-x257 has mentioned it. Warning, spoilers ahead!
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The Dagger . More armour and bigger powerplant than the Defender and much more agile, bigger cargo hold (loot!) and only one gun mount less. It cannot use torpedos but you cannot get torps in Liberty anyway. This is a great ship and fun to fly (I beat the game in it, too).

Ahhh yes, of course. I kept meaning to get one. Only one of two light fighters to interest me (The other being the Drake)
After SP is done I'll probably own it at some point.

Defender dude this is the pattern i used-

DEFUALT--------DEFENDER---------ANUBIS----------EAGLE------------TITAN----------SABRE---------EAGLE (the eagle rocks!!!!!!!!!)

Patriot is the better choice. Loaded right, the patriot can serve you through the entire campaign, while the defender's lack of maneuverability will eventually kill it. The Patriot may carry fewer guns, but it can and will dodge just about all of the enemy fire, so the only hull damage you might ever get is from radiation. Whenever I used a defender in SP, I wound up limping into Leeds with both wings shot off...I never got so much as a scratch in a Patriot.

Dagger is another fine ship, but if you're KOS to the Rougues, it's easier to go with the Patriot.

Reaper: $200,000,000.
Rockets: $100,000
The look on that pilot's face when you launch a full pod of screamers up his tailpipe: priceless