737-900. https://m.youtube.com/watch?v=Mxh8zBCVr64 They have the tendency to tail tip. I hate meeting them as the auto leveler (the wheel attached to the jet bridge that adjusts the height of the jetbridge as the plane rises/lowers) can be spun beyond it's ability to correct as fast as the aircraft adjusts causing the jetbbridge to stop correcting. I stay very close to the jetbbridge during unloading for manual intervention as this is not an uncommon occurrence.

They also have a nesting system in the pit which moves large quantities of bags forward/aft, shifting the CoG rather rapidly. I know CO modified their loading/unloading procedures to minimize this.