Mega Man X2 makes a particularly interesting run as there are many weapons that can be used to increase mobility. These include a grappling hook, a fast mid-air dash, and a weapon that can transform enemies into platforms.
Hetfield90 improves the previous run by nearly 9 seconds with some new tricks and changes to boss fights. See the submission comments for more details.
This run goes for the fastest completion time, only collecting the X-Buster upgrade. TASVideos also has the "100%" run which collects all the parts of both X and Zero.