With the current state of Neon, New Modified, Standard(its been called
everything, I'm talking about the NeoGenesis+ format) being so water
dominated-Kingdra swarms, Dark Blastoises, and Kabulix- of course the
best idea would be to counter these archetypes with lightning or grass
decks.  Now, with Expedition out, there's WATER RESISTANCE for the first
time in history.  I'm talking about the new Meganium, with Soothing
Aroma and Poison powder.  On its own its too slow to be of much use,
however if you use it is a deck with two of these and two Wild growth Meg's,
you can pull off a 2 Energy 40 damage attack with auto-poison and NO
FLIPS.  Also, if both Meganiums are in play, Soothing aroma Meganium only
has to discard 1 grass Energy to retreat! Know what this means?
Meganium Swarm! That's right, bench a Wild Growth Meganium and a Soothing
Aroma Meganium, with another SA Meganium active, using Healing Fields, Gold
Berries and Meganium's power itself, you could get a lot of healing!
This pokemon's high HP almost ensures no OHKOs so you can retreat it and
bring up a healthy SA Meganium, while poisoning and doing 40 Damage to
your opponent every turn!   Of course getting these evolutions out fast
and reliable will take a massive card-drawing engine to do it, however
the new Expedition cards make card drawing all the more easy.  Dual
Ball, Copycat, Oak's research, and old favorites like Breeder/Fields,
Trader, Cleffa and Elm make evolving fast and painless.  Here's the deck I
play at my league:

19Pokemon
4 Chikorita E 50HP
2 Bayleef (N1 80HP)
2 Meganium (N1 Wild Growth)
2 Meganium (E Soothing Aroma)
4 Cleffa (eeeeeeek)
3 Exeggcute (Jungle/LC)
2 Exeggcutor (Jungle/LC)

24Trainers
4 Prof Elm
4 Pokemon Trader
2 Pokemon Breeder
1 Pokemon Breeder Fields
1 Challenge!
3 Focus Band
2 Double Gust
2 Gold Berry
2 Healing Field
2 Time Capsule
1 Super Energy Retreival

17 Energy
17 Grass Energy

(Of course this deck still needs a lot of work but I am using only the
cards I own and not Apprentice so bear with me here.)
Now, with Expedition out the word on the street is that the enviroment
will shift to fighting pokemon, instead of water.  that's sort of good
because some rock pokemon are still weak to grass and almost all
fighting pokemon have big retreat costs, which makes them very weak to
poison.  Meganium's major weakness is the existance of Neutral Shild Mew and
foil Espeon, which will most likely become extremely popular to counter
fighting pokemon.  Fire will also become popular again due to fewer
water types, so play this Meganium now while people still play water
types, and have fun laughing in Kingdra's face!