If your campaign eschews cosmic conflict of the Thor vs Cthulhu variety, and stars instead a bunch of semi-amoral rogues with money on their minds, then how does alignment really fit in? I see it more as a measure of honor and reliability. In a Conanesque swords & sorcery game, it's useful to know who is going to stand by his word and who will betray you the moment it looks convenient. And when it comes to pulpy, morally murky fun, who does it better than Sergio Leone?
Tuco is pretty obviously Neutral. He likes the advantages of working with a team, but saving his own skin is top priority. If you play straight with him, he'll play straight with you - literally risking his neck as long as he gets his cut. But if you betray him and let him live, he will hunt you down, plain and simple.
Angel Eyes, it turns out, is Lawful. When he's paid, he always sees the job through - even if that means killing the man he just finished reporting to. You always know where you stand with him, and you can trust that he'll stick to an agreement. Just watch your back when the deal is concluded.
That leaves the man with no name. He posed as an honest bounty hunter, then double-crossed the towns that paid him by freeing his prisoner. They repeated this scam in town after town And when the money from this scam stopped looking good enough, he abandoned his partner to his fate in the high desert. And let's not forget who betrayed whom when he briefly teamed up with Angel Eyes.
So... which treacherous murdering bastard is your style?