Octillery
Suction Cups
Cannot be forced to switch. Increases chance of encountering Pokémon while fishing.
Type Tier
Water UU
Statistics
Min- Min Max Max+
HP
75
 - 291 354 -
Atk
105
 221 246 309 339
Def
75
 167 186 249 273
SpA
105
 221 246 309 339
SpD
75
 167 186 249 273
Spe
45
 113 126 189 207
Name Item Nature

Physical Attacker

 Leftovers Brave
Moveset EVs
~ Sludge Bomb
~ Rock Blast / Ice Beam
~ Surf
~ Hidden Power Fighting / Hidden Power Ground / Thunder Wave
196 HP / 252 Atk / 60 SpA

Look at Octillery's stats. They absolutely scream "mixed sweeper". Well, here you go. Octoboy is slow as hell, so Paralyze anything that you can, then go to town with its two best attacking moves and a nice STAB Surf. Simple, really. Use Hidden Power Ground / Hidden Power Fighting depending on whether you want to hit Blissey, Snorlax, and Tyranitar harder, or Metagross. Surf keeps Skarmory and Weezing from ruining your fun. Rock Blast is good for Substituters, but Ice Beam keeps Salamence at bay.

Name Item Nature

Special Attacker

 Leftovers / Lum Berry Modest / Quiet
Moveset EVs
~ Surf
~ Ice Beam
~ Flamethrower / Fire Blast
~ Thunder Wave / Hidden Power Fighting
252 HP / 252 SpA / 4 SpD

Pure special sweeping set, or mainly special sweeping with one physical attack put in there. Use Thunder Wave if you don't feel you need a physical move for Blissey and other special walls. Pretty good with STAB from Surf and Octillery's awesome Special Attack stat.

Other Options

Octillery can use Psychic to hit Gengar, but aside from that, not much.

EVs

Put as much as you want into both Attack and Special Attack, with whatever is left in HP. Give it a Brave or Quiet nature, as it's slow already and is going to be trying to Paralyze whatever it can.

Opinion

Octillery is incredibly cool and has awesome attack stats but just isn't very durable. It also is a pure Water, so it has no STAB physical attacks, though Sludge Bomb and Rock Blast are great moves in their own right. Don't use it in standard play, as it just can't survive and trade blows against most OU Pokémon. In UU play, however, Octillery becomes a force to be reckoned with against a team that isn't ready for it.

Counters

If it's low on health, Dugtrio can obviously get it, but Octillery can survive a Choice Band Earthquake at full health, and its Surf destroys Dugtrio. Jolteon, Raikou, and Zapdos will all scare it away, but if you predict you can Paralyze on the switch. In general, anything fast that can OHKO it is going to scare it away.