Suffocate in a Heatran.
Seriously, what was Game Freak eating when they shat out this pitiful excuse for a Pokémon? It has a great movepool—in fact, it's one that extends out ad infinitum—but its stats went down the crapper.
At least Spinda has many uses, which are... yeah I got nothing.
Spinda wishes that it had better stats. And a better sprite. You've gotta admit, it looks ugly. Incredibly ugly. It couldn't possibly be more ugly; if it walked into a fire, it'd look like it just came out of Extreme Makeover.
Now, as soon as it Wishes, you can Baton Pass out to pass the loving Wish to another Pokémon and restore half of its Hit Points... if Spinda doesn't die first writhing in agony from a Luvdisc Tackle. Protect helps stall its inevitable doom, scout for Choice Pokémon, and restore its own health from Wish. How exciting.
Instead of Wishing, Spinda may Calm Mind to rest in peace. Preferably under a grave. One turn should be all Spinda can take, so Hypnosis the enemy. How Spinda can do this is beyond me—you'd think its incredibly ugly features would be enough of a distraction to render its opponents utterly incapable of being hypnotized, but what do I know. Once you're all "set up", Baton Pass out to another Pokémon whose body is made out of muscles instead of paper.
So, what exactly does a Pokemon do when their defenses are so horrible that they can't take a hit? They pray they don't get hit, and that's what this set attempts to accomplish. Bring Spinda in on something that it can force out (good luck with that - you'll need it) and set up a Substitute. Putting that ugly face behind a Substitute will surely make your opponent happy, since they won't have to look at it; however, they are actually in for a nasty surprise. From there Spinda can use either Teeter Dance or Body Slam. Spinda's Attack is so awful that confusing its opponent is sometimes its best way of damaging them; this is where Teeter Dance comes in. Then, Spinda can use its paper body to slam the opponent with Body Slam, betting on the 30% chance of paralysis. Spinda can then Substitute, if needed, hoping for some parafusion. After the opponent is both paralyzed and confused, they will only be able to attack you three-eighths of the time, while Spinda is safely behind its Substitute. Spinda can then fire off Rock Slide, which has an additional 30% chance of causing the opponent to flinch. Hopefully, after this process is finished, Spinda will have (miraculously) actually killed something and still remained intact itself.
If Spinda has Choice Scarf, it outspeeds everything on its teetering legs. Take advantage of Spinda's horrendous face, using it to Trick your opponent (Spinda's face is like a train-wreck; it's horrible, yet you simply can't look away) while you swap their items, hopefully Tricking Spinda's item onto a tank or sweeper that wants to set up.
Now the advantage is in your hands. Hypnosis someone else, and you've just disabled a third of their team. And just as suddenly, Spinda's usefulness runs out. The only thing he can do next is Sucker Punch the Pokémon who otherwise resist Spinda's STAB moves. If you're not sure about predicting with Sucker Punch, Faint Attack and Psycho Cut are options over Sucker Punch.
Whenever you think you're about to die (read: fairly common), make your Spinda Endure all the insults at his unsightly physique and survive at one HP. Send it off Flailing and crying madly against its attackers for a 200 Base Power attack multiplied by STAB. Baton Pass out to give another Pokémon a Speed boost, knowing that their trainer finally chose them instead of Spinda. Faint Attack or Sucker Punch that them there Ghosts.
If you're good at prediction, this is where Spinda's black belt training finally pays off. Whenever your opponents dawdle instead of attacking Spinda like they should be, let fly a Focus Punch to ram their faces in and make them as ugly as Spinda. If you can manage to anger them into physical attacks, Counter back their attack; thanks to rigorous training in secluded mountain temples and the Focus Sash around its waist, Spinda always survives the first attack.
Once you're weak or the enemy knocks your Focus Sash away, use the last two moves to flail around before you die: Return to try to reclaim Spinda's former glory, and Faint Attack to fight sneaky.
Disable causes the enemy to become completely appalled at how much Spinda sucks horribly in every aspect of everything, and be unable to use the last move it did out of pity.
Checks and Counters
Mawile takes anything of Spinda's—except Focus Punch—and Intimidate turns Spinda's limbs into jelly. Relicanth takes the same moves, and it can Head Smash Spinda and irreparably fracture its skull (not much difference with or without a head, anyway). If Relicanth has a Choice Band, it can come in on Trick Spinda relatively safely, and if Relicanth has Sleep Talk, it can take Hypnosis. Sudowoodo makes like a tree and ignores everything Spinda throws at it.