I was playing Black Mesa last night as well, I downloaded it on Desura. Not sure if that's why the loading screens take about 30 seconds each but it's a bit jarring. Really, really good quality though, I'm astounded that a mod can be that good. Also tried To The Moon last night but had to stop because it was making me sad.
All this talk of Cazadores is making me want to go back to New Vegas. In both of my full playthroughs of it I think I kind of ruined the game for myself by focusing on sniping, I never really got up close with a Cazador. Actually no, I tell a lie, when I was exploring early on in a playthrough I encountered one and never wanted to encounter one again, so I guess that's why I wanted to snipe everything instead. I think I started a melee/pistols only playthrough before I stopped again last time so I might start over with the same focus.