Ok, so, I have 2 things to ask. 1. I was looking for the page of one of these threads that had the cheats to get the super gravity gun on any level. I know I have to go collect it in that one level then I use ___________________ To go back to a level and then type ___________________ to get the gravity gun. anyone help please?

2. How do I enable the console

to enable the console check the box in the keyboard settings.

To elaborate:

Esc > Options > Keyboard Settings > Advanced > Enable Console.

As far as Cheats and Console Commands go, just look it up. The only commands I can tell you are those I'd use on my server in CSS, like the very, very occasional NoClip when nobody's around ;)
That's because I've never had any need to use the console whilst playing HL2.

Try this site, for example. Here's the cheats page, maybe you could find something there. There's a bunch of useful commands.

THanks guys, I've got the console working and found a thread for the grav gun.