I have a Macbook Pro and when I click with the trackpad, it will occasionally act like a double click. This happens whether I physically click the trackpad or if I just do a tap to click. I have tried changing the double click speed to no avail. It might be a hardware issue, but the fact that it happens when I tap to click leads me to believe it is at least not a mechanical issue (still possible an electronics/cable issue with the trackpad). I have also reset the NVRAM and the SMC (not sure why it would be an issue with those but I'm attempting everything). I'm on Yosemite.
Try disabling tap to click in the trackpad settings. If you're MacBook has the new vibrating force touch trackpad you could try to disable the force click and haptic feedback. Otherwise it may be a hardware issue.
I am having the same issue, and for now the only solution I found was to use a usb mouse. I think the problem began with 10.10.4, but I am not sure. It only happens to me with Chrome and Steam mostly.