I've been playing Doom II for the past few days, and I've never really used a melee attack at all. The berserk seems like it'd be awesome, but I always end up switching to a shotgun once I get in a real fight because I take so much damage when trying to actually punch mutants. Even the chainsaw seemed next to useless, to the point where I just ignored that it existed.

When are these melee attacks worth using? Are there any techniques I should keep in mind when using them? Or were they added just to have more cool items and not to actually see serious usage?