I know it's not that original, but I still think Avalanche is the best physical Ice move. Know of anything I could use to replace Waterfall/Aqua tail?
The drawback with avalanche is that it forces you to go last, even after focus punch (which when it does hit first causes flinch 100% of the time)
If you use Dragon dance then the speed boost would be moot
Dive works because your only vunerable to surf or whirlpool , which most wouldn't use on gyarados in the first place, I'd still suggest waterfall.
Earthquake is a must because of electric types
Move (pokemon that are completely resistant to its move pool)
Ice Fang (shedinja) [get super effective on many other sweepers, works well with expert belt]
Stone edge (Breloom) [warning low acc]
Payback(Breloom, Cacturne, Nuzleaf) [doesn't force you to go last but if you do its powered up]
Outrage (shedinja) [powerful but locks in for a few turns]
Bounce[covers all pokes, STAB, but also has low acc]
Some normal type Move here (shedinja, O-Giratina)[pick what you want for effect]