You probably all already found this out but you can get Half Life 2: Deathmatch and Half Life 2: Lost Coast for free. For Nvidia people you get these plus a Portal Demo and Peggle Extreme!
ATI
https://www.steampowered.com/ati_offer1a/
Nvidia
https://www.steampowered.com/nvidia/
HAVE FUN!
Cool, I wanted to try deathmatch and now I’m dowloading it.
Damn, and I found out about these YEARS ago
I’m scared of clicking it,everytime I do a bunch of pages open up infinitely :[
awwww,thought a free copy of hl1 was up for grabs 
so i used it and i had all this stuff, but where is my peggle extreme ?
edit; yeah ofc it was free already, it was all free, so what the deal here, an offer with stuff that was always free ?
I have an NVidia card and it says my system doesn’t meet the requirements. So it’s bullsh*t.
does hl2 deathmatch come with sdk? if so, can you play black mesa off that without having to buy hl2?
no
buy the un-free ones
Well, i also dont know if its already said in another Thread, but there is a list for all free steam games in the steam forums:
I downloaded Track Mania and Codename Gordon. Free and fun to play 
Wow TYVM! i always wanted to get DM, but didnt want to pay. Thanks so much!
yeah… i knew bout this YEARS ago.
Man, I knew about this shit years ago…you guys are damn late. Really late.
I remember this offer from a long time ago… You are pretty damn late to this, but it’s still a good offer.
Founded in 2004, Leakfree.org became one of the first online communities dedicated to Valve’s Source engine development. It is more famously known for the formation of Black Mesa: Source under the 'Leakfree Modification Team' handle in September 2004.