Since it's the regigigas event. Normal

[wellwisher]

Since it's the regigigas Event, two normal Pokemon.


...no, wait, I forgot about one.

Now, Normal pokemon can be quite unerappreciated because they don't get many type advantages. On the flip side, they dont get many type disadvantages.
They take no damage from ghost moves. but double damage from Fighting moves.
Normal pokemon also deal no damage to ghost attacks. 50% damage to rock type pokemon, and 50% damage to Steel pokemon. (Which makes Aron and it's evolution family murder to Normal pokemon, as it takes 25% damage from normal attacks, which are what Normal pokemon can STAB with. and 25% of a 150% attack is only 37.5% damage.)

Normal pokemon rarely get placed on teams, because there are usually better, type pokemon to replace them. Not to mention the fact that when building a pokemon team, you should try to compensate for as many weaknesses as possible, while putting in pokemon to take down the enemy team.  

[Nadian]

Meanwhile, on the competitive front...


Blissey
The highest HP stat combined with a Special Defense stat tying for 11th amongst *all* pokemon make this pokemon a complete wall for pretty much any special attack. In the standard metagame, you can even focus your nature and EVs into toughening up Blissey's abysmal defense stat and still use it to sponge up special attacks. Combined with a reliable healing move (in the form of Softboiled) and taking Blissey down is no picnic.

The real problems, though, are that Blissey can accomplish this task and still provide other sorts of assistance to the team. Thunder Wave, Toxic, and Sing allow it to throw around status effects. Aromatherapy allows Blissey to cure status effects for its entire team. Even if it finds itself in trouble because of a status effect, Blissey can fall back on one of its abilities (Natural Cure) to heal itself.

But Blissey is also somewhat dangerous on the offensive front, displaying quite a variety of offensive types with access to Ice Beam, Thunderbolt, and Flamethrower if it wants to deal direct damage. With Blissey's other ability, Serene Grace, moves such as Thunder look excellent with their boosted 60% paralysis rate.

More interestingly, Blissey can function on the offensive spectrum without investing any IVs in its attack stats thanks to Seismic Toss and Counter. The former allows Blissey to whittle away at opponents usually faster than they can. Meanwhile, Counter plays right into the common Blissey countering strategy: attacking the weaker physical defense side and failing to KO in one hit could result with twice the damage returning to you (and since Blissey has an incredible amount of HP, chances are your pokemon can't handle it.)


Snorlax
Yet another defensive pokemon that sees lots of use. Similar to Blissey, Snorlax is defensive on the special front with a high HP, but in a show of independence, Snorlax also has a high physical offense. Because of this combination, Snorlax's favorite mode of attack is probably the "Curselax" set. Pokemon don't want to hit that spongy special defense so they would want to aim for the physical defense. However, Curse will raise that defense as well as the good attack stat at the cost of lowering Snorlax's already horrid speed stat. Not a bad trade-off.

About the biggest problem Snorlax has is that he doesn't have any reliable recovery moves. Rest is pretty much his best option. Not necessarily bad, but in the fast-paced 4th gen environment, that could be just the opportunity for your opponent to get some much needed stat boosts.


Porygon-Z
Tied with Alakazam and Darkrai for the 8th highest Special Attack stat in the game and boasting a good movepool (and turning every Normal-type attack into, effectively, a Super Effective attack thanks to Adaptability) causes Porygon-Z to see a lot of usage. Its biggest downside is that its speed stat is fairly poor. It can outrun some stuff, but most of the time it's working around this problem. (Choice Scarf, Agility, Substitute, etc.)

Looks like the biggest downside is that Porygon-Z desperately wants a fighting-type special attack ; lots of suggested sets fall back on Hidden Power to provide this.


Togekiss
Togekiss is yet another bulky pokemon that sees lots of usage. You'll usually see it using Serene Grace to its most annoying ; causing paralysis (Body Slam or Thunder Wave) and flinching to death (Air Slash.) Even beyond that, Togekiss has an excellent movepool that allows it to throw quite a variety of strategies around. Being part flying-type, Togekiss also gets access to the reliable healing move Roost.




Some other notables (that I felt like mentioning):

Ambipom
Discover the pain of Fake-Out, boosting by Technician, STAB, and Life Orb... all behind a high attack stat...


Porygon2
Surprisingly filling a completely different (defensive) niche that its evolved form (Porygon-Z) can't.


Smeargle
Boasting one of the biggest movepools of all pokemon thanks to Sketch.


Bibarel
Although the Bidoof / Bibarel line is generally good for a laugh, Bibarel has some odd abilities that have allowed him to find his own way of the ninja.

Unaware allows Bibarel to stop some otherwise dangerous monsters by allowing him to ignore opponents' stat boost when attacking / defending. Combined with Taunt + Super Fang (which allow Bibarel to take down walls), Bibarel is surprisingly capable of shutting down your opponent's strategy.

Simple, Bibarel's other ability, allows it to build up stat boosts much faster than other pokemon. Using this, Bibarel can participate in both the offensive and defensive fronts (although usually not both at the same time.)  

[wellwisher]

So, Normal pokemon, they act as Walls.
except for a select few which actually work for offense. Is the weakness to Fighting a large weakness?  

[Nadian]

wellwisher

So, Normal pokemon, they act as Walls.
except for a select few which actually work for offense. Is the weakness to Fighting a large weakness?

Kind of ; it's a common attacking type, but I think Normal is generally a useful defensive type because that's its only weakness. It pretty much lets the stats dominate the outcome a bit better.