Well UU being my forte I will give you the best sets I know for that tier.
These are my personal favorite sets:
Mew @ Leftovers
Ability: Synchronize
EVs: 252 HP / 252 SpD / 4 Def
Calm Nature
- Substitute
- Roost
- Night Shade
- Will-O-Wisp
With its massive 404 HP stat, it makes 101 HP Substitutes -- which, with its Special bulk, are hard to tear down. Burning anything but Guts Heracross pretty much makes this set unstoppable.
Umbreon @ Leftovers
Ability: Synchronize
Calm Nature
EVs: 252 HP / 252 SpD / 4 Def
- Heal Bell
- Foul Play
- Wish
- Protect/Yawn
Cleric /Special wall. Pretty standard Umbreon set.
Miltank @ Leftovers
Ability: Thick Fat
Bold Nature
EVs: 252 Def / 236 HP / 16 Spe
- Stealth Rock
- Seismic Toss
- Milk Drink
- Heal Bell
Another Cleric with some utility, and can set Rocks. Bold nature and no Atk investment stops Foul Play from beating it up.
Weezing @ Black Sludge
Ability: Levitate
Bold Nature
EVs: 252 HP / 252 Def / 4 SpD
- Pain Split
- Will-O-Wisp
- Substitute
- Clear Smog
This set focuses on crippling and stalling while clear smog stops it from being set up on by CM Suicune and the like.
I have found the Mew/Miktank core to be effective as Normal and Psychic cover each other well. Also Weezing/Umbreon are a pretty sweet matchup as well.
Hope this helps :)