I use the following 5 Pokemon in Ubers:
1: Shuckle (F) @Leftovers
Impish Nature (+ Def, -Sp. Atk)
EVs: I forget the exact spread... but I go to 559 in both defences, so that's 252 in Sp. Def for sure, and because of Impish, I can invest more in HP than I would've normally been able to.
Power Split / Toxic / Rest / Bug Bite
Power Split is really awesome against offensive Pokemon, as it shares my horrible offensive stats with them, meaning Bug Bite usually does SOMETHING. I use Toxic to wear Pokemon down, then Rest when I need healing greater than Leftovers provide.
2: Whimsicott (M) @Leftovers / Choice Scarf
Calm Nature (+ Sp. Def, -Atk)
EVs: 252 in both Defences, 4 in HP.
Switcheroo / Leech Seed / Protect / Substitute (with Choice Scarf)
Leech Seed / Protect / Substitute / Stun Spore (with Leftovers)
You may have been thinking that a Choice Scarf was pointless on a Prankster Whimsicott, but it means that I can mess up an opponent's strategy with a Choice Scarf. I think it's better than using Band or Specs because it could potentially make them an offensive threat to me. Scarf allows me to keep Whimsicott up. Priority Leech Seed + Leftovers heal me after Substitute, and Protect stalls another turn, adding up to more HP recovered. Stun Spore slows attackers, and forces switches. Also, there's no limit to how many Pokemon can be paralyzed.
Memento: This is if I am for SURE going to die, or just want to force a switch. I use this in place of Stun Spore.
3: Blaziken (F) @Nothing / Focus Sash
Adamant Nature (+ Atk, -Sp. Atk)
EVs: 4 HP, 252 each in Atk and Spd.
Hone Claws / Hi Jump Kick / Acrobatics / Blaze Kick (w/o item)
Hone Claws / Hi Jump Kick / Blaze Kick / Protect (with Focus Sash)
Hone Claws boosts my Attack even further, and increases my Accuracy so that I don't get Hi Jump Kick's recoil as much. Blaze Kick is the Fire STAB, and Acrobatics is for additional coverage. I don't have an item as Acrobatics' power is doubled if I'm not holding anything. However, I can easily be KO'd, so a Focus Sash is a good idea, in which case I drop Acrobatics and put in Protect.
Baton Pass: With Speed Boost, and a Hone Claws boost, Blaziken can effectively create a fast physical sweeper that can use inaccurate attacks easily.
4: Smeargle (M) @Focus Sash / White Herb
Bold Nature (+ Def, -Atk)
EVs: 252 HP, 252 Spd, 4 Sp. Def.
Spore / Shell Smash / Baton Pass / Substitute
Spore / Mind Reader / Sheer Cold / Protect (Don't use this with White Herb)
The first set uses Smeargle's capabilities as a Baton Passer. Spore is an accurate way of putting an opponent to sleep, Shell Smash raises Atk, Sp. Atk, and Spd by 2 each, at the cost of -1 in Def and Sp. Def. White Herb ignores the defensive drop, so you could easily pull another Shell Smash off without lowering Defences too much. Substitute is always useful to Baton Pass.
The second set uses Spore to make the opponent fall asleep, then hits with a OHKO move. Sometimes these are banned, though, so this version of Smeargle isn't the best. Note that this set is completely blocked by any Pokemon with Sturdy.
5. Aron (Lv. 1) @ Shell Bell
Jolly Nature (+ Spd, -Sp. Atk)
Endeavor / Protect / Aerial Ace / Sandstorm
This is one of the best FEAR Pokemon out there, as it doesn't have to use a Focus Sash to get to 1 HP. Endeavor drops the opponent's HP to 1, and preferably, Sandstorm finishes them off. Aron recovers ALL it's HP due to the Shell Bell, and is ready for another Endeavor. Note that some Pokemon are resistant to Sandstorm, so Aerial Ace is a good alternative as it never misses, so Pokemon that spam Double Team, etc. or have Sand Veil are always hit. Protect is just protect. Aron needs another filler move.