I have spent the last few hours devising this team for NU. In NU, there are so many things to choose from it made this very hard for me. Bu I did it, so here it is!
Cacturne @ Life Orb
Ability: Water Absorb
EVs: 4 HP / 252 Atk / 252 Spd
Role: Physical Sweeper
When I was first thinking of making a team, I decided on using a Dark/Ghost core due to perfect synergy. Therefore, here's the first half. Just your standard SD Cacturne. Seed Bomb for STAB, Sucker Punch for second STAB and priority, and Drain Punch for coverage and to heal off Life Orb recoil. Standard physical sweeping EV spread.
Lampent @ Eviolite
Ability: Flash Fire
EVs: 4 Def / 252 Sp. Atk / 252 Spd
Role: Special Sweeper / Spinblocker
The second half of my offensive core. Lampent provides near perfect coverage for Cacturne and can take some hits because of Eviolite. Fire Blast and Shadow Ball for STAB, Energy Ball for coverage, and Sub so Lampent doesn't get statused (especially with paralysis, as it's already slow as it is). Standard special sweeping EV spread and all that.
Wartortle @ Eviolite
EVs: 252 HP / 252 Def / 4 Sp. Def
Role: Physical Wall / Spinner
I had Cacture and Lampent, might as well get that Fire/Water/Grass core going. Rapid Spin to spin away hazards (especially Stealth Rock for Lampent), Scald to do some damage (especially in Torrent range) and to hopefully get burns on stuff. Haze is for stopping setup sweepers in their tracks, and Foresight so Wartortle can't be stopped from spinning by a Ghost-type. Wartortle is weak to Electric and Grass, both of which are primarily special. Therefore, it made sense to max out Defense as I don't want it taking those moves.
Kecleon @ Leftovers
Ability: Color Change
EVs: 252 HP / 4 Def / 252 Sp. Def
Role: Special Wall / Stealth Rocker
In NU, most of the Stealth Rockers there are Steel and/or Rock, which hurts this team's defensive synergy. However, Kecleon, a Normal-type with only one weakness fits right in as Lampent can take hits for it. Stealth Rock is the most important/best move in the game, gotta have it. Thunder Wave is for crippling things, Return for STAB, and Recover for reliable healing. Kecleon has a base Special Defense of 120, the same as Arceus, so it only made sense to max out it's Sp. Def.
Eelektross @ Expert Belt
EVs: 252 Atk / 212 Sp. Atk / 44 Spd
Role: Mixed Attacker / Cleanup (sort of)
Great attacking stats at both ends of the spectrum, decent bulk, a moveOCEAN, and no weakness. Eelektross can fit onto almost any team, and it certainly fits on mine. As opposed to being a special sweeper or a physical Coil set, I decided to take a mixed approach. Wild Charge is there for a powerful STAB and Flamethrower for coverage against Grass and Steel-types. Giga Drain and Drain Punch are there both for coverage and so Eelektross can heal off Wild Charge recoil from the physical and special sides.
Swalot @ Black Sludge
Ability: Liquid Ooze
EVs: 252 HP / 144 Def / 112 Sp. Def
Role: Mixed Wall / Toxic Spikes Absorber
Let me tell you right now. This thing's ANNOYING! It can phaze you out by locking you into a move with Encore or by using Yawn so your Pokemon doesn't fall asleep. Sludge Bomb is for STAB and the 30% poison chance is very nice. Pain Split is to ensure it never dies.
So here you go! Look at it and tell me what you think of it.