OpenMW brings a host of improvements to their Open Source Engine!

Three years of development have led to a brand new release of OpenMW! If you're not familiar, OpenMW is an free and open source re-implementation of Bethesda's classic The Elders Scrolls: Morrowind.
This release improves AI and Pathfinding, Animations, Configuration and VFS, Game Save format, and Gameplay improvements.
AI & Pathfinding
This version includes upgrades to the AI actors in the game with new spell logic, optimized pathfinding, and improved behavior including taunting, combat, and more!
As they described in their post:
We taught creatures to drink potions, introduced laws against lycanthropy and vampirism, and told Snowy Granius that his skeleton buddy misses him a lot.
Animations
They added a new "super -flexible" animation interpolation state machine that helps smooth out the transition between two distinct animations. Before this update, the animations would just jump between keyframes resulting in a jarring "cut."
ESM Format for Save Games
This update has changed which save game formats are compatible. Anything save game from version 0.45.0 or before will be rejected. This is in an effort to streamline the code and polish the saving/loading feature.
Gameplay
There are some significant gameplay changes here–all in an effort to bring OpenMW closer to the Morrowind experience.
The first big focus is how melee combat works. Quote:
Trying to get [melee combat] right was a focus for this release, and we replaced the physics-based hits of previous releases with Morrowind’s more simple scanning of the player’s surroundings based on a hit cone defined by the game settings. It comes with replicating some quirks, such as NPCs being unable to look “up” or “down” to attack, or collision box offsets relative to the actor positions not being used.
Graphics
The graphics pipeline continues getting improvements as well. They've added occlusion of rain and snow–meaning it will no longer precipitate through ceilings.
They've improved lighting in many subtle ways that should minimize pop-in and look more like the original game, and provide better specular effects for point lighting.
And there's a ton more. The post is several pages long with details about the update and things I don't have time to touch on!
Check out their release notes here and give the game a spin if you're so inclined!