Full Disclosure: This list does not have any specific order. This is mainly just me listing off what I like about Sonic characters. I will say though- Silver and Omega are my top 2 :)
Silver the Hedgehog
“To kill someone to save the world, Is that really the right thing to do?”
Silver is one of my favorite characters in the series- Everything about him gives off "cool" vibes from his psychokensis down to his design.
His design is one of my favorites! It's not super overly-detailed (like many of the character in the comics, for example). His silvery fur pairs well with his backstory, giving him a "ghost from the future" vibe that I like. Along with the blue boots, his color scheme also contrasts with Shadow, who has a black/red color scheme and is known to have an edgeiness to him. Silver's design has some silliness to it (Someone said his quills above his head looks like a pot leaf), but the series has always had some amount of silliness to it. Overall, Silver's design is fantastic for what it's supposed to do.
One thing that definitely sucks about him is the fact he always appears in crappy games. His debut was the dreaded Sonic '06! '06 had it's lion's share of issues, but Silver got the short end of the stick- His levels were full of bugs and weren't very clear on where to go or what to do. He moved egregiously slow, which is offensive for a Sonic game!
Although he has playable roles in Sonic Rivals, and several minor spinoffs, his guy never got his due. I hope one day he gets his chance to truly shine!
Vector the Crocodile
"Once we start a job... we finish the job! That's our policy! We're Team Chaotix!"
Did you know that this guy was concieved as early as the first Sonic game? During the early development of the original Sonic the Hedgehog, there was going to be a band that would play as part of the Sound Test, dubbed the "Sonic the Hedgehog Band". Even though the band didn't make the cut, he would later make a comeback as the head honcho of the Chaotix Detective Agency, alongside Espio the Chamelion and Charmy the Bee. Over the years, he would outgrow the Chaotix box he's was placed in and appear without his teammates. Silver and Vector even teamed up in a racing game!
What do I like about Vector? He's a surprisingly well fleshed-out character with a lot of stuff going for him. He loves money, music, and food. His dream is getting rich. He has a short temper and a tough exterior. He has a strong moral compass and prefers to keep things legit. And, most importantly, he loves and cares about his friends!
Plus, he's funny.
E-123 OMEGA
"Worthless Consumer Models!"
Meet E-123 OMEGA: As the last of the E series robots, he was created by Dr. Ivo 'Eggman' Robotnik to be locked away in a vault (alongside everyone's favorite black hedgehog). After being reactivated, he swears revenge on the good doctor for locking him away and seeks to destroy his entire army. And... that's it. He is little more than a killing machine who defected from his master and seeks to prove that he is the STRONGEST™ and MOST POWERFUL™ robot ever designed.
Even though he is a character who lack depth (like Vector and Silver), I don't think he needs it- He's a cool robot! Why would he need to have an arc?
I like E-123 OMEGA because he's cool. He doesn't try to be anything else. He's just a cool robot, and I like cool robots.