A great single-player mod is Point of View, you play as a vortigaunt fighting through Black Mesa, has a great story and good level design.
http://halflife.multiplayer.it/pov/
Oh my god you can listen to the class sounds. Scout sound awesome, and annoying!
"Yo I need help cappin'!"
"Am I gunna have to capture this thing by myself?"
"DEFEND THE FREAKIN POINT!"
"What am I gunna have to defend this thing by myself?
"This did not just happen!"
"This sucks on ice."
"No...
Actually, that sound is played over the idle metropolice radio, you get chances to hear it at the beginning of the game up until the apartment raid.
Heres a related one: remindermemoryreplacement.wav
"Reminder: Memory replacement is the first step towards rank privilages"
I bet once metropolice...
I have some tips:
When you need to be precise when you position something on the ground, duck. You'll move slower and it will become easier. (Freeze that prop first!)
For moving contraptions freeze everything until after you've welded it all, that way you can avoid welding something to 2...
I wonder what, nay, how the vortigaunts would think when one of them gets crabbed, they're sorta hive-minded after all. This raises the question weather vortigaunts have enough combined will-power to resist headcrabs completely, or if another vortigaunt will come relieve his brethren ASAP, maybe...
If you haven't already, download GCFScape, go to your program files/steam/steamapps or program files/valve/steam/steamapps whatever, and open 'day of defeat source.gcf', these are all the games files, here's where everything non user-specific is stored. You can browse through the sounds there to...
The best way to free the unfortunate enemies from their torment is to end their broken lives as quickly as possible!
BOAHAHAHAHHAHAAAH! *BLAM!* *BLAM!*