Unown

Unown's forms seem to have some meaning; resembling that of ancient hieroglyphs.  They are always stuck on walls.  When one Unown is all by itself, nothing seems to happen, but when there's more than one Unown, it said that an odd power of some sort emerges.

Unown has more forms than any other Pokemon with a total of 28 different variations.  One for each letter in the alphabet, and an exclamation point and a question mark.  Unown has a poor base stat of 48 for HP, Defense, Sp. Defense, and Speed.  It makes me wish Unown really was "unknown", because this is a really pointless Pokemon to have in the game.  Its Attack and Sp. Attack stats have a base of 72.  It seems like Game Freak doesn't want use Unown at all.  It also makes one wonder if this Pokemon was just made for the anime.  Again, Unown's stats are horrible.

Only one move.  Unown has only one move.  It's Hidden Power.  Its type and power is based off of the Pokemon using it.  To find out Unown's Hidden Power type, go to the Pokemon center in Mistralton City and ask a guy by the counter.  He'll tell you what type Unown's, or any other Pokemon's Hidden Power type.  Use Google to find more info on Hidden Power, because there's too much for me to explain in one post.  Having only Hidden Power makes Unown sink like a rock.  

Unown's ability is Levitate, which means you're immune to Ground-Type moves.  I guess it's okay, because you're immune to Fissure and Earthquake, but Unown isn't weak to Ground-Type moves, so the ability isn't really that useful either, and don't leave out the fact that nobody hardly even uses Unown anyway.  

Of all the Psychic-Types, Unown has to be the worst.  It's really cool that it has all those forms, though, not to mention the fact it's so cute!  But in battle, Unown is worthless.

Shedinja

Shedinja is a discarded bug shell.  Peering into the crack on its back supposedly could steal one's spirit.  It manages to stay in the air, but doesn't flap its wings at all.  Shedinja doesn't breathe.

This is a really weird Pokemon.  You only have 1 HP.  No HP ups or anything can change the fact that you only have 1 HP.  You have low Defense, Sp. Attack, Sp. Defense, and Speed stats.  Shedinja's highest base stat is its Attack.  It only has a base number of 90.  Low stats and 1 HP adds up to a pretty messed-up Pokemon.

Shedinja should stay Physically based because it has a low Sp. Attack stat.  Some good Physical STAB moves could include X-Scissor, Shadow Claw, or Bug Bite.  You can use Heal Block, which is a good move.  If you use it, the target can't have HP or status conditions restored or cured.  Its a useful move, because ever since they've introduced the launcher for WiFi battles, battling has become so different.  Your opponent also can't use moves like Recover or Wish.  Other good Physical moves Shedinja has would be things like Night Slash, Dig, and I guess Aerial Ace.  But in conclusion, Shedinja has a limited movepool.

Your ability is Wonder Guard.  Only Super-Effective moves can hit you.  This may seem like a good ability, but you have 5 Super-Effective weaknesses.  The maximum amount of Super-Effective weaknesses a Pokemon could have is 7 total.  5/7 weaknesses- Wonder Guard isn't exactly the most helpful ability, but I guess it's better than nothing.

So Shedinja has low stats, a pretty limited movepool, and only one HP.  Not the best Pokemon out there, but he's cool looking.

Dustox

Dustox is attracted to bright lights.  When it flaps its wings, dust is scattered around.  But this is a toxic powder that can be dangerous to other Pokemon.  At night, Dustox is known to strips all the leaves off the trees that are alined amongst a boulevard.
Like Wurmple's other evolved form Beautifly, Dustox suffers from low stats.  Low HP, Attack, Sp. Attack, and Speed.  This makes Dustox very vulnerable to any super-effective moves or moves with a base power of 150 or something like that.  Dustox has a fair Defense stat, but it has a higher Sp. Defense stat.  However, when your highest stat only has a base of 90, you're really not going to see much use with Dustox, I'm afraid.
It has a few decent moves- like Quiver Dance, a move that makes your Sp. Attack, Sp. Defense, and Speed stats go up.  If you get away with using this move 2-3 times in battle, it'll make Dustox fairly stronger.  However, you have low stats as it is, so Dustox can be taken out really easily.  You can teach Dustox Moonlight, a move that restores HP.  If you use Sunny Day to make it sunny in battle, then you'll recover even more HP.  Dustox has a few okay STAB moves, like Silver Wind, Bug Buzz, Sludge Bomb, and U-Turn.  Dustox has a limited amount of options in its movepool, making it a hard Pokemon to work with.
Its ability is the best thing on Dustox you'll get.  It's Shield Dust.  Shield Dust blocks secondary effects from an attack.  For example, Flamethrower is a move that does damage and for its second effect, it might burn its target.  Well, if Flamethrower was to be used on you, then you would only take damage; you would not be burned.  This does not count for moves like Will-o-Wisp or Swagger.  It's a good ability on Dustox, because it needs all the help it can get.
Dustox has low stats, a shallow movepool; everything on it adds up to a Pokemon that isn't exactly the most useful.  If you want to use Dustox, use it for Musicals, Contests, Pokeathlons, anything besides battling!

Beautifly

Despite its graceful looks, Beautifly can get a bit aggressive at times.  If it's disturbed when collecting pollen, it'll jab anything it sees as a foe with its long, thin mouth.  If you want to see one, just leave a potted flower by an open window.
In the first two games Beautifly appeared in, which were Pokemon Ruby Version and Pokemon Sapphire Version, this was one of the Pokemon that you can easily find near the beginning of the game.  Unfortunately, this means that it has low stats.  Low HP, low Defense, low Sp. Defense, low Speed- Yikes!  It has okay Attack stats, and its highest base stat- Sp. Attack.  However, it only has a base of 90, meaning it isn't exactly the strongest.  Low stats doesn't make Beautifly the most useful Pokemon.
Beautifly has some decent moves.  It can use Giga Drain.  It's a great move.  It has a good STAB move called Silver Wind.  It doesn't have the highest base power, but there's a good chance it might raise all of your stats a little bit.  It can also use Quiver Dance, which makes your Sp. Attack, Sp. Defense, and Speed stats.  If you can manage to use it a couple of times in battle, it'll make Beautifly a bit stronger.  Quiver Dance works out for any Pokemon that can learn it.  If you want to give it a strong move, try using Hyper Beam.  It can use Morning Sun, which restores HP.  If you use Sunny Day, making it Sunny in the battle, restoring more HP when you follow Sunny Day with Morning Sun.  Beautifly doesn't have the biggest movepool, but at least it has some good moves.
Beautifly's ability is Swarm.  It ups the power of Bug-Type moves.  Not too bad of an ability- Beautifly needs all the help with its stats that it could get, and the ability does just that.
To be honest, I love Beautifly's design- but it just has low stats and all that.  It could use some improvement.

Flareon

When Flareon breathes in air, it is heated in a flame sac inside Flareon's body to a really hot fire over 3000 degrees Fahrenheit.  It will fluff out its collar of fur to decrease its body temperature.
Flareon is the Fire-Type Eeveelution; in other words, an Eeveelution is an evolved form of Eevee.  Flareon has low HP, Defense, and Speed stats.  It kinda sucks, because you need Speed for lots of serious battles.  Low Defense stats makes Flareon weak to Physical moves.  Yikes!  Low HP also sucks, because when you take a hit, you won't have lots of HP, and therefore easily susceptible to strong moves like attacks with a base power of 150 or Super-Effective moves.  Flareon has okay Sp. Attack, and has really high Sp. Defense and Attack stats. High Sp. Defense is good, but you still don't have lots of HP stats in order to take a Super-Effective hit.  High Attack stats are really good, too.
If you want to give Flareon a really strong and Physical Fire-Type move (to get that Same Type Attack Bonus) you're going to have to be flexible.  It's strongest Physical Fire-Type move is Fire Fang, with only a base power of 65.  Some people don't really use moves with a base power of 65 or lower, so they might want to use the Life Orb to make Fire Fang stronger.  Otherwise, Fire Fang is an okay attack.  In 4th Gen., Flareon could learn Superpower by move tutor.  It's really useful in tough battles.  It's just not really good because Flareon has more Special Attacks than Physical Attacks.
Flareon's ability- Flash Fire.   You don't take damage from Fire-Type attacks.  When you are hit by one, the power of your Fire-Type moves increase.  It's just like Water Absorb or Volt Absorb.  People know not to hit Fire-Types with Fire-Type moves because THEY'LL JUST BE NOT VERY EFFECTIVE!  It's a poor ability on Flareon.
So Flareon doesn't add up to a really great Eeveelution.  It's useful for some things, but definitely not the best Eeveelution or Fire-Type at all.