http://www.serebii.net/pokedex-dp/139.shtml
Type: Water/Rock
Abilities: Swift Swim, Shell Armor
70 HP / 60 Attack / 125 Def / 115 SAtk / 70 SDef / 55 Speed
Physical:
Bite
Spike Cannon
Rock Blast
Frustration/Return
Thief
Stone Edge
Gyro Ball
Rock Slide
Waterfall
Knock Off
Special:
Mud Shot
Brine
Ancientpower
Hydro Pump
Ice Beam
Blizzard
Water Pulse
Hidden Power
Hyper Beam
Surf
Bubblebeam
Aurora Beam
Wring Out
Support:
Tickle
Protect
Rain Dance
Toxic
Hail
Captivate
Rest
Sleep Talk
Swagger
Substitute
Spikes
Haze
Toxic Spikes
Supersonic
Sets:
Omastar @ Leftovers
Trait: Swift Swim
Modest Nature
252 SAtk / 48 HP / 208 Speed
-Rain Dance
-Surf / Brine
-Ice Beam
-Ancientpower
It's a shame that he does not get Grass Knot, but with this set, he can always finish stuff off with Brine, since, if the opponent is below 50% health, Brine's power doubles and becomes 130. With Rain Dance and STAB, it is very very powerful. And with Omastar's above average special attack, Brine is an effective finishing move. Surf is there if you are not sure. With Omastar's good defense power, it can come in and help eliminate Sandstorms that may be plaguing your team, but watch out for Earthquakes and Grass Knots, and whatnot.
Type: Water/Rock
Abilities: Swift Swim, Shell Armor
70 HP / 60 Attack / 125 Def / 115 SAtk / 70 SDef / 55 Speed
Physical:
Bite
Spike Cannon
Rock Blast
Frustration/Return
Thief
Stone Edge
Gyro Ball
Rock Slide
Waterfall
Knock Off
Special:
Mud Shot
Brine
Ancientpower
Hydro Pump
Ice Beam
Blizzard
Water Pulse
Hidden Power
Hyper Beam
Surf
Bubblebeam
Aurora Beam
Wring Out
Support:
Tickle
Protect
Rain Dance
Toxic
Hail
Captivate
Rest
Sleep Talk
Swagger
Substitute
Spikes
Haze
Toxic Spikes
Supersonic
Sets:
Omastar @ Leftovers
Trait: Swift Swim
Modest Nature
252 SAtk / 48 HP / 208 Speed
-Rain Dance
-Surf / Brine
-Ice Beam
-Ancientpower
It's a shame that he does not get Grass Knot, but with this set, he can always finish stuff off with Brine, since, if the opponent is below 50% health, Brine's power doubles and becomes 130. With Rain Dance and STAB, it is very very powerful. And with Omastar's above average special attack, Brine is an effective finishing move. Surf is there if you are not sure. With Omastar's good defense power, it can come in and help eliminate Sandstorms that may be plaguing your team, but watch out for Earthquakes and Grass Knots, and whatnot.