Frank Sobodka especially. Great character plus all his outbursts were note worthy imo.
Also Brother Muzone

Stringer Bell is perhaps my favorite character but he's fucked. Initially I thought he'd be far more dangerous on the streets than Avon but damn, nearly all of his executive moves fizzled and will probably lead to him getting killed. The D'Angelo hit, dealing with Proposition Joe behind Avon's back, and the failed Muzone hit. That last fuck up especially struck me as odd; he had to know Omar was too smart for that. Now all his enemies have heavy dirt on him.