I'm not on Signal Beam's side, everyone. Look, I'll even point out that HP Ice and Signal Beam do the same damage to Shaymin, and other stuff like Sazando.
HP Ice is the best most of the time; Signal Beam and Shadow Ball may be better in few circumstances. (Like your team has an Ice Shard Poke or something)
Thunderbolt hits Salamence, Dragonite for neutral. Hydro Pump hits Garchomp, Flygon (who is almost non existent due to Randorosu) for neutral. Latias, Latios, Onokonosu, and Sazando are the dragons who need to be dealt with Coverage moves. There's ton of grass types. I'll list the main stuff. The Pures (Erufuun, Shaymin, etc.) are dealt with basically any coverage move. Roserade and Venusaur are only harmed by HP Ice. Breloom and Birijion (the new Grass Fighting Legend) are also only harmed by HP Ice.
Abomasnow, Ludicolo, and Celebii are weak to Signal Beam (Well, Ludicolo is hit by Thunderbolt anyways). As for Shadow Ball... Has slightly more base power than the other two (yes, without STAB), hits Dragons equally hard as Signal Beam except Sazando. Can't hit Mebujikija, Cacturne and Shiftry, but no one cares about them. Oh right, and Nattorei, which is a big minus for Shadow Ball. As for Parasect, Wormadam and Hahakurimo, no one cares either. Jumpluff, Tropius and Skymin is killed by Hidden Power Ice much more than the other two. Rotom-C doesn't matter. Torterra is badly hurt by Hidden Power Ice. Oh right, I forgot about those Egg/Coconut/Whatever things. But they don't matter, do they? (PS I know their names, just joking around)
I mean, HP Ice is useful, but not all the time. Still, most of the time.
HP Ice > Signal Beam > HP Dragon > HP Ground > Shadow Ball > Dark Pulse > HP Fighting > HP Flying
IMO. Other Hypothetical (almost useless) HPs listed.
