FlareArmed,
Yes, there are a few...a small charter company I worked for some time ago allowed the F/O, if he was the flying pilot, to make the RTO decision...it should be noted that all the F/O's were very experienced.
As to the decision to G/A, have always insisted in line training First Officers, that if they do not like the situation developing, to use their initiative when they are the PF....ie; don't like the picture, do something about it, not just sit there waiting for it to get worse......go around.
Better safe than sorry.