What is your favourite legendary pokemon signature move? For me, i l like origin pulse the most. The animation and the background us just so cool and intimidating! Even when kyogre roars when using origin pulse is intimidating as well. The move just leaves quite an impact its hard not to say wow. Precipices blade is just meh compared to origin pulse.
Roar of time. Mostly because when I was a kid I used legendaries on my main team (I don't anymore as I find them too op for the main game). In Diamond I loved to use Dialga and spam Roar of Time I loved the idea of everything being destroyed by a roar.
Probably because all of those are the signature moves for mythical Pokemon and not legendary Pokemon. OP did forget to include the signature moves of the following legendaries, though:
Latias (Mist Ball)
Latios (Luster Purge)
Heatran (Magma Storm)
Regigigas (Crush Grip)
Giratina (Shadow Force)
Cresselia (Lunar Dance)
White Kyurem (Ice Burn)
Zygarde (Land's Wrath)
Speaking of Giratina, Shadow Force is my favorite signature move. Mainly since Giratina is my favorite Pokemon. Roar of Time and Oblivion Wing are pretty cool as well though.
Of the ones listed, I probably have to give it to Sacred Fire. I really like Ho-Oh and Entei, and adding that move to Entei's movepool in Gen VI made it more useful. Oblivion Wing was a close second though, because I like that it both deals damage and heals for 75% of the damage dealt. It has 20 less power than Sacred Fire though, so it's less appealing.
Of the ones not listed, it's a tough call between Dark Void, Judgment, and Techno Blast. I think I'd rank it Techno Blast > Judgment > Dark Void though, as despite only being able to use 5 types, Techno Blast is more powerful than Judgment and I like Genesect's design more than Arceus'.
Diamond being my first game, I was in awe when I first met Dialga. I love his design and his signature move, Roar of Time. It really helped me through the Elite Four, especially since I was the biggest noob. But I've come a long way, and that Pok?mon and move reminds me of how far I've come in Pok?mon! Oh the feels over a move :')