Lanturn
[SET]
Name: Light in the Dark (Agility SubChargePetaya)
Move 1: Substitute
Move 2: Agility
Move 3: Charge Beam
Move 4: Surf/Ice Beam/Hidden Power Grass
Item: Petaya Berry
Nature: Modest
EVs: 4 HP/252 SpA/252 Spe
This is Lanturn trying to be the Empoleon. Of course, they shouldn't be compared, because Empoleon is few classes higher than this Lanturn thanks to the bigger Special Attack and Torrent, but Lanturn should fill role of SubPetaya Sweeper pretty nicely in UU. However, Lanturn has some features that make him slightly better than Empoleon. Firstly, after Agility Lanturn is faster than Empoleon. Both of them got immunities, but Lanturn heals its HP when hit by Electric move. It also has less weaknesses. But leave it, to the point.
The key of this set is to set up three Substitutes to get to the point, where Petaya Berry will activate. At that time you must use Agility and it would be really wonderful if you manage to hit some things with Charge Beam and probably (60% chance) get a Special Attack rise, what will double you SpA at 25% HP point. Then, when Lanturn is really fast, you can attempt to sweep. Keep your Sub up as long as it will be possible to stop potential quick damage and, basically, status moves, which completely ruin your attacking turns, especially those, which deal damage every turn. So, after the set-up, you should look quite nicely. Let's analyse the moves now.
The first two moves are obvious, they mustn't be changed. Some players may have doubts about replacing the Charge Beam with Thunderbolt for more Base Power, but remember that Charge Beam has a big chance to raise the Special Attack, while you will be using Thunderbolt defeating stronger enemies may become an issue, because you won't have enough power to kill them, when they simply take you down with one move, since you're at low HP. The fourth move needs cogitation. Surf is a pretty nice STAB move, but it doesn't provide coverage for Grass types, which are all resistant to this version of set. Tangrowth, Exeggutor, Ludicolo, Venusaur and enemy Lanturn wall this set for years and end your fun quickly. That's why Ice Beam appeared as an another option. It makes an problem for all Grasses, except Ludicolo, and forces them out. Killing Dugtrio also isn't a problem, since you have enough SpA to take it down and you are faster. But then Blaziken and Houndoom become safe and can kill you. Also enemy Lanturn is an issue. But there appears third alternative: Hidden Power Grass. And again. All Grass- and Fire-types can safely switch and set up, while Lanturn will fail to do any form of decent damage to them. Fortunately, foe's Lanturn stops being a problem. Any version of this set can't do much to Chansey, who can break your Sub with Seismic Toss and kill you with status move.
Summing up, the fourth move depends on your choice. For me, Ice Beam looks the best, because it provides the best coverage and there's small heap of Pokes who block this set. If you decide to run Hidden Power Grass, use 31/30/31/30/31/31 IV spread, or else you will have to spend extra 4 EVs on HP.
[ADDITIONAL COMMENTS]
Here are some damage calculations for set-up Lanturn:
+1 Surf vs. 212 HP/0 SpD Gastrodon: 50.7% - 60.1% HP
+1 Ice Beam vs. 32 HP/0 SpD Ludicolo: 38.5% - 45.6% HP
+2 Ice Beam vs. Calm 136 HP/252 SpD Tangrowth: 100% HP
+2 Surf vs. Calm 0 HP/252 SpD Chansey: 25.5% - 30.6% HP
+2 Ice Beam vs. Calm 40 HP/252 SpD Lanturn: 17% - 20% HP
+2 Surf vs. Careful 252 HP/216 SpD Swampert: 47% - 55.7% HP
+2 Surf vs. 0 HP/4 SpD Jolteon: 91.9% - 100% HP
+3 Critical Surf vs. 252 HP/0 SpD Blissey: 64.4% - 76.1% HP
The best teammates to this set are those, who have Earthquake as a main attacking move and also can surprise other Grasses with Fire or Flying move. Actually, there's one, that has this property. Nidoking can get rid of all annoying pokes that wall this set. Special Attacking or Mixed Tangrowth also laughs at guys who are taken to stop Offensive Lanturn. He can put them to sleep or kill them with Power Whip, Earthquake or Hidden Power Fire.
In OU he needs a strong physical attacker, for example Choice Band Gallade can take down Blissey with Close Combat, also Breloom with Focus Punch and other guys, who are big threats for all best tanks.
Counters to this set have been mentioned repeatedly, so these are:
Tangrowth, Exeggutor, Ludicolo, Venusaur, Lanturn for set without Ice Beam, while Lanturn, Ludicolo, Blaziken are safe with the set without Surf. These are guys who can stop it in UU.
In OU, the best counter is Swampert, who doesn't care of either Surf or Ice Beam. Also Blissey and other Tanks aren't afraid of damage from this Lanturn.
