Various ways to get health (and one or two I may not know of) such as the packs on the ground, the wall First Aid machines (a green "First Aid" sign often signals one is near) as well as activating the soda machines (1 HP each time). Also you can break open wooden crates which may have ammo and/or health and/or shield packs. But be careful...you may need one to move and jump on in order to get up in some air vent or something. Speaking of which, some grate covers can be busted open with the crowbar so you can crawl in the air ducts, if you haven't figured that out already. You can interact with the world in various ways. Butane cannisters and crates labeled Explosive can be shot a few times to detonate. Note how they are often near a couple stronger enemies...or you can carry it, toss and BOOM.
BTW, of course it's "good"...it's Half-Life!
Edit: I think I missed the Revolver. Is it before the freezer? Simple yes or no is good, trying to avoid spoilers.