I was just thinking, and I came up with a list of things that you will never hear Sonic say, but would be really cool if you did: 
"Don't PISS me off man, I'll Spin Dash yer ass." 
"Look kid, you think turning into Super Sonic is all a game, but it's not. Do you have any idea what Chaos Emerald over-exposure has done to me, physically and mentally? DO YOU?!" 
"I swear to God I am going to go postal on the next idiot gamer who calls 'em 'Coins'." 
"Tails...Tails, I'm starting to think you're misinterpreting the type of 'relationship' we have." 
"What's that? Robotnik's taken control of South Island and turned all of its helpless animal inhabitants into robot slaves to do his evil bidding? And this means what to me?"