Sky Mesa puts you back in the shoes of Gordon Freeman. Sky Mesa is a little map pack for half life that has 4 new playable maps. There are no new weapons nor enemies in this mod. (There are some new textures though.) Just the same ol'half life weapons. There is however, a cameo from an unused HL1 monster.
While it's not going to win awards for the most eye-catching mod available on HL, I have to admit, I have seen far worse ventures by more experienced modders and worse first attempts by amateurs.
The gameplay was straightforward for the most part but the enemy placement felt random, making most firefights chaotic.
I hope the modder has learned some valuable lessons while creating sky mesa, and as a HL mod, it's far from terrible, but unless you are desperate for a HL mod, you might be disappointed.