Kostya Tszyu, was a great straight puncher, it's why he handled southpaws so easily, he'd catch em time and time again with the straight right down the middle. People don't talk about his speed but his two punch combination was lightning q0uick.
All punches are straight to a certain degree. Even hooks are just straight punches coming from a different angle because in case you haven't noticed we can't bend our arms below the elbow
Julio Cesar Chavez had a beautiful right hand, straight as an arrow, and he could double it with ease. He could also mix it up with overhand rights, and especially loved finishing his combos with a vicious left hook to the body. But that straight right got him in the door.
Arguello's right hand flew as straight as an arrow and hurt like one too. Zarate's 2 was quick, straight and looked more like a rear handed jab. Mainly used to follow up a jab, as a unexpected lead, or hold them in place for the following left hook/uppercut. Doesn't sound dangerous until you remember his regular jab shook guys without the hip rotation and weight shifting...
The Loma sidestep allows him to throw a 'straight' punch from the angle a hook comes from or a hook from the angle a 'straight' punch comes from. If you stand in front of someone and shoot them in the head or arc your arm round to the side of their head and shoot them the trajectory of the bullet is always straight not curved and it's the same with a hook and every other type of punch. The punch will always end up being straight by the time of impact, whether it be a straight right or left hand, a jab, a hook, or an uppercut so every punch is technically a straight punch.