Hexen: Beyond Heretic

In the GZDoom version, just go into the video options menu, scroll through to the correct aspect ratio (or to "all"), and select your resolution. Extra anomaly: It is playable, but it has an interesting bug. This is the first game using the Doom engine where some of the weapons are oriented to the side instead of the center. This can produce strange effects for these weapons, like a disembodied floating arm, or a swinging axe coming out of nowhere.