Immortality?

I do indeed...

right click on your Half-Life icon which I suppose you have on your desktop, where it says Target:, change it to where it looks something like this C:\SIERRA\Half-Life\hl.exe -console
Then open up half-life and there's a new option labeled Console, click on it and type in, sv_cheats 1, then exit the console.
Start a new game and press the ~ key to bring down your console, typing in the following codes will grant you special cheats...
/god = self explanatory
impulse 101 = all weapons and ammo(do this multiple times to fill up on ammo, repeat do refill)
noclip = fly

for other cheats visit Cheating Dome