What is it? I clicked the crowbar which changed my cursor and that was it.

Start clicking on stuff, You'll find it :)

I was clicking around like mad, nothing happened and I gave up

Try clicking on the various enemies or people.

I tried clicking on everything, I just gave up lol

Click on Gordon and the Xen Alien after you have gotten the crowbar.

haha thanks I would have missed it ! so fun to hear those sounds !

Do tell...

Click crowbar and start hitting ...stuff.