This is one of the dumbest threads I've ever seen on this forum. What does that question even mean? The gear that pulls the hardest is the lowest one you can use (without going over redline) for whatever speed you are at.
Regardless of how the question was phrased I think most of us admittedly know what he means.
He likely simply meant, what gear gives you the greatest amount of G-Force for the longest period ? The time factor makes first gear pretty useless.
Keeping in mind that higher wind resistances are going to dampen the experience at higher speeds, the answer mostly depends on the speed and RPM cap.
I always prefer to keep my RPMs beneath 4 or 4.5k and cap around the speed limit which may be 40-45 mph or 60-65 mph for highway on-ramps.
If I'm capping around 40mph, then second is going to be the most fun.
For higher speeds I'm not going to have enough RPM so it will have be 3rd. Regardless I'm not one of those people that does rapid lane changes and I'm almost never out late anymore so haven't gotten the chance to safely pull a third gear.