Ryan's PokAnalysis
Uxie is the little pixie that could. It's got many tricks up its sleeve, with a surprisingly large movepool. The reason that it finds itself in LU or RU is that there's many Pokemon that pull off most of its tricks better than Uxie. So why would you use this Pokemon? Again, back to that movepool.
Uxie is loaded with support options and the stats to use them. Stealth Rock, Thunder Wave, Memento, the list goes on. That gives it a niche in LU/RU that makes it a valuable partner. However, if you expect some kind of attack capability from Uxie, it's there...barely. It's attacking stats are mediocre, but it does have Calm Mind to help that out. Another thing to note is that it has no recovery outside of Rest, which would help its awesome bulk out a ton. Don't let that turn you away, though. It's versatility means that your opponent doesn't really know what to expect with this Pokemon.
Abilities
Levitate: Uxie's only Ability but a much appreciated one. Psychics can stand to get more resistances anywhere they can get them, and this certainly helps.
Move set time. I'll do one that others haven't done
Helmet Head
- Substitute
- Calm Mind
- Psychic / Psyshock
- Thunderbolt / Hidden Power [Fighting]
Item Attached: Leftovers
Ability: Levitate
EVs and Nature:
96 HP / 188 SAtk / 224 Spd
Modest Nature (+SAtk, -Atk) / Timid Nature (+Spd, -Atk)
Sub Calm Mind Uxie isn't as oddball or outclassed as it sounds. It's got bulk coming out of the wazoo so you should be able to set up a Calm Mind or two without fear of death. Substitute is held up by pretty nifty defenses. Psyshock is your main STAB and makes sure Pokemon like Blissey pay for trying to wall you. Thunderbolt provides nice coverage with Psyshock even though Krookodile will be immune to both attacks. If you don't like immunities stopping you, try Hidden Power [Fighting]. It - oh yeah. Spiritomb.
...
Well, just go with whichever one you feel like!
Other Options for Uxie
A lot. Amnesia, Choice items/Trick, Fire/Ice/Thunder Punch, Heal Bell, Magic Coat, Memento, Psych Up, ResTalk, Safeguard, Shadow Ball, Yawn, Zen Headbutt, Mental Herb.
Amnesia astronomically boosts Uxie's Special Defense. Too bad it doesn't have reliable recovery, or else this would get way more use than it does.
Choice items, although you may think other Pokemon make better use of them, are usable thanks to Trick giving Uxie a way to surprise and cripple non-offensive threats.
Elemental Punches are in Uxie's arsenal. However, it does not have a way to boost its Attack outside of Swagger / Psych Up, making this option weak.
Heal Bell is one of a slew of support moves that will come in handy, removing status problems.
Magic Coat is an option because many people see Uxie as hazard-setting fodder. It also bounces back Taunt, and that's extremely important.
Uxie is probably the bulkiest user of Memento in the game (besides maybe Cofagrigus). This provides it with an excellent niche that it can take good advantage of even in Ubers, as proven last Gen.
Psych Up nabs stat changes, perhaps perfect for beating a set-up sweeper.
Rest / Sleep Talk works with Uxie's incredible bulk to make it a potent staller. However, choose carefully what moves go with it.
Safeguard, unlike Heal Bell, stops status problems from surfacing. Very useful on a stalling set but otherwise I prefer Heal Bell.
Shadow Ball is an option to replace Substitute on the Calm Mind set. Which is useful as that set get stopped by too much.
Yawn forces a switch or puts the opponent to sleep.
Zen Headbutt is a substitute for Psychic on the main support set if you want U-turn to do more damage. That and getting walled by Steelix and Alomomola doesn't bother this Pokemon at all.
Mental Herb can be useful as Uxie absolutely hates being Taunted, and the herb is a get-out-of-jail-free card.
Partners
Fighters are arguably the best partners, for Dark-types are the worst enemies, and they will end Uxie pretty quickly with a combination of Taunt and STABs. Lucario benefits greatly from the Stealth Rocks and paralysis that Uxie throws around, being able to KO opponents far easier under said circumstances, 4x resists Dark and gets Justified, and isn't as bothered by Taunt. What else isn't bothered by Taunt? Choiced attackers, like Heracross, who effortlessly pummel Uxie's enemies. If we're talking about the lower tiers, perhaps look to Scolipede, Hitmonlee, and all that. Most of them learn Rock-type moves, so that's useful for handling Bugs like Venomoth.
Countering Uxie
If it can learn Taunt, it can counter Uxie. 95 base Speed isn't quite enough to do it justice, although it is faster than most Taunters in the tier. Of all the Taunters, Whimsicott laughs at it as either Taunts Uxie or stalls it to death with Encore + Leech Seed. Mandibuzz can Taunt and phase it with Whirlwind (the rare Nasty Plot set will beat Uxie most if not all of the time). Really, any Dark-type will do a number on it. Bugs like Venomoth can murder it, but STAB can hit a lot of them hard. But basically, just stick to Taunt. That move is the one that does the most damage to Uxie and its vast versatility.