Nightmare House 2
Research and Development
Portal Prelude (Not for Half-Life 2, but so what? 
)
^SHIT FUCKIN SUCKS.
seriously. It was bad. I made myself play through start to finish bc thats just what i do if iām going to start something. It was painful. āVery, very longā and āvery, very badā sums up this mod pretty good.
[HL2, HL2:EP2, Portal mods]
My singleplayer faves, best from top to bottom:
(1-4 are fucking legit and I thought deserved numbering)
- Nightmare House 2
- Research and Development
- Portal Prelude
- Minerva Metastasis
Mission Improbable
Precursor
Outpost 16
Radiator
Riot Ī»ct
The Citizen
Korsakovia
Dear Esther
Provenance
aaaaand Checkerboarded Hopes 2
The Citizen was okay, but I really disliked both the voice acting and level design for the most part.
I liked NH2 and AoM: DC, I liked horror games, but I liked Point of View, Azure Sheep, and Precursor too.
Someone said They Hunger. I completely forgot about that. It was an amazing Half-Life mod. So was that one russian mod that greatly modified the engine and somehow made it look good. Sadly I cant remember the name 
Iām waiting for BM and Ivanās secrets mod
For Half Life 2, probably Minerva. For any game, probably the Dark Mod or maybe the Nameless Mod.
If weāre naming mods for any game, Nehrim for Oblivion, hands down.
Counter-Strike. If you mean not able to get on Steam then SSH: Mod Messup #1 : WTF
HL1 - USS Darkstar, POKE 646, They Hunger, Azure Sheep, Challengerās Deep
HL2 - Research and Development, Minervaā¦havenāt played as many HL2 mods 
Let me seeā¦hmmā¦:
They Hunger
Invasion
Poke 646 + Vendetta
Lifes End
Brave Brain
Force of Evil
Azure Sheep
ā¦there are many ā¦I havenĀ“t played any of HL2 mods yetā¦