One I use for a bit of fun occasionally, and for certain mixing purposes, is Waves “NX”. This is designed to simulate a mixing room, spatially and dimensionally, with the ability to adjust speaker placement, adjust headphone response (preset EQ curves for a small list of common headphones found in mixing/tracking setups).
It can make listening on headphones feel a lot closer to using speakers, particularly if paired with a head-tracker, so that the position of the sound changes as you move your head.
With the RAAL-requisite SR1a the effect is even more convincing.