Half-Life 2: Short Stories is a team working on a group of modifications that take place in the same realm. A lot of the focus is on the story and gameplay, new innovative set pieces and puzzles. After the release of the first episode of Human Error, the team is planning to release more episodes and expand the characters and the world.
One of the best mods for half-life 2 on this website. Most mods you play as Gordon or a rebel but this one let's you play as the civil protection. Now this mod has new weapons, enemies and items. I won't say what they are because you should try this for your self, now this mod is short about 1-2 hours long but its so good I would replay it again