What's your favourite skill in db series?

[GTX]

I. myself like dragon punch because the cool effect
2.full powered blast because its uniqueness and it's used as technical attack

[Lunatic Fringe]

The Makankosappo. Really like the set-up, the execution, and the fact that it's a Piccolo move certainly helps. After that, nothing beats a good 'ol Kikoho.

[LuckyCat]

Warp Kamehameha. Combines two of Goku's best moves into an extreme spectacle.

[AS_Saiyan]

I gotta go with Kamehameha as my favorite. I'd be lying to myself if I'd say it doesn't. I remember the countless times I did it as a child trying to pull some energy ball out of my hands.
Second would be Kienzan, just because it is so awesome that with this move, even the weakest person could beat the strongest enemy.

[FortuneSSJ]

Easy one.
https://www.youtube.com/watch?v=GqUwzvuUgA4

[B]

Kienzan. My favorite character invented it, no other technique is like it, and it looks hella cool dudebro.

[Soppa Saia People]

KI
KO
HO
It's so cool.

[LightBing]

Gekiretsu Kōdan (Light Grenade), with the Final Flash variation used by Vegeta on Namek a close second. Such a shame both of them failed to kill their target.

[fadeddreams5]

Super 13's nut punch.

[Cetra]

Final Flash

The name alone destroys worlds and gives kids nightmares.

[Lord Beerus]

The Kienzan. Can cut through anything, and if you're skilled enough, you can control it, too.

[Neo-Makaiōshin]

The classic Kamehameha.

[Vijay]

Shunkan Idou Kamehameha

Its such an epic attack, which would inflict high degree of damage to any Non-regenerating foe

[swimtrunks]

Instant transmission for sure.

Reminds me of my favorite X-Men character Nightcrawler.

[voltlunok]

Favorite skill? 16? Rocket Punch! Thank you 16. Though that is more a robot/mecha thing in general. What can I say? I like mecha!

[TheZFighter]

Kamehameha is the obvious one. My friends and I spent many a lunchtime on the school playground practising our Kamehameha Wave. It is synonymous with the series.

Honourable mentions to Tenshinhan's Tri-Beam, which looks amazing and is incredibly powerful, Krillin's Destructo Disc, also looks amazing and is devastating, Yamcha's Spirit Ball, which again looks great and is so cool because you can direct it and make it hit multiple times, and finally Yamcha's Wolf Fang Fist, because yet again looks great and because you can really see that move being applied in the real world.

[Khin]

A coin toss between Final Flash and Makanposappo.

[MajinMan]

The kamehameha. It's used in so many great moments and has a classic feel to it. The runner up would have to be the final flash.

[Kunzait_83]

Kienzan and Makankosappo win for sheer inventiveness and creativity. And for brutality (cutting/piercing techniques).

Kikohou just for being such a damn powerhouse and for the huge risk and toll/strain it takes on the body of the user (one of my favorite under-appreciated wuxia tropes) and for having a cool-ass hand gesture. The Kaioken ranks alongside it for similar reasons (minus the hand gesture obviously).

Soukidan for just being plain damn fun (and for being fairly Zu Warriors-esque). Way too underused considering how strategically useful it could be in a fight.

Shishin no Ken/Bunshin (body division) for pure memorable weirdness: no matter how many times such a technique crops up in wuxia, it always feels so surreal.

Ghurd being able to stop time by holding his breath and Ginyu's body change, also for creativity and weirdness.

Cell's giant Ki barrier is simply the coolest of all the Ki barriers we see in the series, and I'm an inexplicable fan of Ki barriers for some reason.

Vegetto's giant Ki lance for being the coolest of all the Ki-produced weapons we see (I'm also big on Ki-generated weaponry).

Virtually everything Gotenks ever uses for the pure "WTF?" factor, with special mention going to Boo's rendition of his Kamikaze Ghosts in the anime for being able to also use techniques like the Kamehameha and Masenko all on their own as they give chase to their target.

Boo's Genocide Attack for how fucked up the premise of it is and for how cool it is visually.

Those are the ones that spring most immediately to mind offhand, but there's definitely others.

This series has a LOT of really inventive supernatural martial arts techniques: I've never really been on board with the criticism that it relies too much on generic giant Ki blasts. Sure its got a TON of those as well definitely, but it also peppers in more than its fair share of fun, unique, and downright odd doses of of Toriyama-ified wuxia moves. Its plenty balanced enough in that regard.

[Polyphase Avatron]

This one was always cool: http://dragonball.wikia.com/wiki/Imprisonment_Ball