This episode's depiction of a warp core being ejected from a Federation starship was the first time that such an event was shown up close.
This is the first time we see the extravehicular suits in the series.
While B'Elanna and Tom are floating in space, B'Elanna mentions suffering from space sickness during the Starfleet Academy space simulations. Worf mentions suffering from the same affliction right before he fights the Borg on the exterior hull of the Enterprise in the film Star Trek: First Contact (1996)
The title and concept of 'Day of Honor' was used by a whole series of Star Trek novels.