Hyper Beam can work OK as a secondary move. Most common time to use it would be when you're facing a slower opponent that is *going* to ko you *this* turn and you have nothing on the bench that can realistically come in against it and your normal moves just aren't going to do the job. You may as well cause as much damage (and maybe take it out) before you go.

Also, sometimes it's just more important to cause more damage in one hit *now*, especially against healers and sappers. Naturally, if you cause similar damage with STAB attacks, don't bother with HB, but any advice about HB applies to such things as Blast Burn, which because they *can* be supereffective, are a touch more useful. I've never regretted putting Frenzy Plant on my Venusaur, for example, since her special attack options are so limited.