What modern ball is similiar to the original ebonite gamebreaker?

I am thinking roto grip rumble. Both solid covers, rg 2.4/2.5, core shape close.

Any professional input would be helpful.

Not even close, while I have a general disdain for Ebonite and their substandard balls, the Gamebreaker is a Top 5 ball, ever. I think the most similar ball would be the IQ Tour Solid, but that ball doesn't have near as much motion as a Gamebreaker.

I have had a Gamebreaker and currently have a Motiv Covert Revolt.  For me, the balls are very similar.

Second on the AMF Darkness.  It gives me the closest reaction I have had to the Gamebreaker.  Length is similar and total hook is about the same as when the Gamebreaker was released the only difference is the Gamebreaker was a tad sharper on the back end not a ton but it is a slight difference.

Actually I got a very similar look from my IQ Solid as the game breaker.  Very smooth off the break point.  IQ is stronger shell out of the box, but put 4000 on it and let it polish to the lane. 

RG numbers are little different but shape wise and amount of hook, I would tell you to look at the new Brunswick Melee Cross. Had gamebreakers galore when they were out and in today's line for that same look I look at the Cross and Hyroad Solid (didn't look at the numbers on that)

I would have to second the Melee Cross and toss in the Radical Yeti Unleashed. The numbers on the Unleashed are close, no doubt the cover is stronger. The Radical drill sheet is spot on for reaction shape too. So you could put your favorite drilling on or pick one from the sheet and know it's going to perform as advertised.