Disclaimer: Harry Potter belongs to J.K. Rowling
So, this is how I imagine the sorting. I got the idea from a pinterest post.
All eyes were turned to the squirming boy on the stool. The hat was partially covering his face but they could see his worried frown. The seconds seem to crawl by.
Sirius Black was especially interested in this student. He could barely see over the cluster of heads. He half-rose from his seat, only to be stopped by a comforting hand on his shoulder. James gave him a sympathetic look and Sirius sat back down, realizing there was nothing he could do.
By now a good minute had passed. A smile slowly spread across Sirius' face, as if the verdict had already been announced.
Finally, the hat came to life and a single world echoed through the hall. "SLYTHERIN!"
He sadly nodded and James squeezed his shoulder. And yet, despite his sorrow, Sirius continued to smile as Regulus took the hat off and raced over to the cheering table clad in green and silver
"Sorry mate." Remus murmured.
Sirius waved his hand and remarked, "Ah, I knew he was going to get sorted into Slytherin."
His friends stared at him, unable to hide their confusion.
"Then," Peter whispered, "Why are you smiling?"
"Because," Sirius proudly said, "The hat hesitated."
Regulus was scared. He was going to get Sorted, and he didn't know what to do. He wanted to be with his brother, but he knew he couldn't face the abuse at home for the desicion.
You would do well in Gryffindor you know. You are brave.
"Not brave enough." he whispered.
Are you sure? You could do well there.
Regulus looked up at his brother, who was being pulled into his chair by his friend. The hopeful expression on his face. A minute passed before he decided. "I can't." he face was sorrowful.
Very well. SLYTHERIN!
As Regulus went to sit with his new house, only one thought echoed in his head. Coward… Coward… Coward Coward Coward.