There are many health items in Doom. But none of them can heal you over time. I know this has been done a lot of times, but this is RegenPacks.
From best to worst:
The Small regeneration pack:
Time: One Minute|Health: 3 points per second.
The Regeneration Pack:
Time: 2 Minutes|Health: 6 points per second.
The Regeneration sphere:
Time: One Level|Health: 10 points per second.
RegenPacks.zip