Tropius
Chlorophyll
Speed doubles in sun.
Solar Power
Loses HP in sun. Special Attack increases 50%.
Type Tier
Grass / Flying UU
Statistics
Min- Min Max Max+
HP
99
 - 339 402 -
Atk
68
 154 172 235 258
Def
83
 181 202 265 291
SpA
72
 162 180 243 267
SpD
87
 189 210 273 300
Spe
51
 124 138 201 221
Name Item Ability Nature

Swords Dance

 Leftovers / Life Orb Chlorophyll Adamant
Moveset EVs
~ Swords Dance
~ Leaf Blade
~ Aerial Ace / Roost
~ Earthquake
6 HP / 252 Atk / 252 Spe

The main reason you would use this set is with Sunny Day support, boosting Tropius to 402 Speed. With a Swords Dance, Tropius' stats are essentially 340 HP / 516 Atk / 202 Def / 210 SpD / 402 Spe, which could definitely sweep an unprepared team. Leaf Blade gives Tropius a powerful attack, while Aerial Ace and Earthquake provide useful coverage. This will probably not work in OU, though. If you want Tropius to last a little longer, Roost works well—Tropius will lose or ameliorate a number of weaknesses while still hanging on to a Ground resist.

Name Item Ability Nature

Choice Specs

 Choice Specs Solar Power Modest
Moveset EVs
~ Leaf Storm
~ Energy Ball
~ Air Slash
~ Hidden Power Fire
252 SpA / 6 SpD / 252 Spe

This set is not as dependent on Sunny Day, but it still really likes it, as sun will raise Tropius' special attack to 400, which Specs will then raise to 600. Further, it boosts Hidden Power Fire, making Steel-types fear this set. Chlorophyll is still an option for this set, as Tropius won't complain about being very fast.

Other Options

You can try to set up Sunny Day yourself, but chances are you'll be kicked out immediately after setting it up. It's best to let somebody else do your dirty work for you, particularly with Heat Rock.

Opinion

Tropius is a unique Pokémon that certainly got a lot of new options in DP—3/5 moves in the SD set, and 3/4 moves in the Choice Specs set, not to mention Swords Dance and Choice Specs themselves, as well as Solar Power, are all completely new. Whether these options are enough to make Tropius usable is another story; low speed, a crippling Ice weakness, and average STAB are problematic. Still, Sunny Day support works to make Tropius a good consideration.

Counters

Without sun, Tropius is fairly mediocre, so Tyranitar, Hippowdon, and Abomasnow, as well as Rain Dance, are good ways to put a shade over Tropius' hopes. The other way to kill Tropius is with a fast Ice user—Weavile, for instance. Also, Stealth Rock will do a good 25% to Tropius.