If you were a Gym leader and had to choose a type

[JarJar]

yeah it should be 2-4 pokemon for gyms..

[Devicho]

Ghost because ghost Pokemon are awesome motherfuckers.
Mismagius
Froslass
Spiritomb
Gengar
Dusknoir
Banette

[des]

electric cus im yellow

also all the pokemon start with the letter d

[Cshad]

Devicho there is a disturbing lack of Rotom in your post.

I'd run a Steel/Rock/Ground team, basically people who benefit from Sandstorm, unfrotunately, most ground/rock/steel pokemon also have a very low Sp.Def.
I think I'm gonna try this later;

Hippowdon
Gliscor
Registeel
Tyranitar
Magnezone
Metagross

This could probably use some tweaking, but oh well. I like residual damage, and Swampert deserves a place somewhere, as well as Scizor, oh well.

EDIT: Ryperior is very very tempting as well.

[8-Bit Squirrel]

Dark because there hasn't been one in the games yet (Elite Four don't count)

Houndoom
Absol
Tyranitar
Spiritomb
Sharpedo
Honchkrow

[Vipershark]

if we're going by r/b/y stats then definitely psychic as it rapes everything

[Cshad]

Anything faster than a Psychic pokemon or Chansey is capable of taking them out/stalling with ease

Psychic wasn't unbeatable in rby

[Sol]

I'd probably choose Normal.

Smeargle
Zangoose
Porygon2
Furret
Persian

These Pokemon choices might suck but I'm not one of those crazy competitive players, I use Pokemon because I like them. I especially like Smeargle on this list, he's actually my favorite Pokemon. :)

[Zac]

These Pokemon choices might suck but I'm not one of those crazy competitive players, I use Pokemon because I like them.

ditto, only I do play competitivly so my pokemon lose alot

[Vipershark]

I don't play competitively so I don't ev train or care about natures, etc
I just get the strongest moves and level my stuff to 100 and just tank my way through everything

[Alpha Six]

pokemon that look cool and take names

Zangoose
Zangoose
Zangoose
Zangoose
Blaziken
Zangoose

[JoshR691]

I think you forgot about Zangoose, Tyvon

I'd probably have a Normal type Gym

Munchlax
Snorlax
Ambipom
Delcatty
and who can forget Smeargle

[GrooveMan.exe]

Ghost/Electric Gym. As always.

Magnemite
Shuppet
Sableye
Magneton
Rotom (Normal, Cut, or Fan)

I'm not so sure about levels or moveset. I'd be about mid/late game, and give out a Charge Beam TM upon defeat.

[Zee]

My choice is of course, Water

Starmie [Sea Incense]

Spoiler

(o) Surf
(o) Psychic
(o) Thunderbolt
(o) Ice Beam

Tentacruel [Poison Barb]

Spoiler

(o) Sludge Bomb
(o) Ice Beam
(o) Knock off
(o) Surf

Lanturn [Wise Glasses]

Spoiler

(o) Surf
(o) Signal beam
(o) Discharge
(o) Aqua Ring

I'd hand out the TM Hydro Pump, permit trainers to use Surf outside of battle and grant the victors the Mercurial Badge.

I do play competatively, and even won a local tournament (which, by the bye, has me hating Gengars) but my team is more than just this, so I figured I'd only mention these three.

[Vipershark]

I know a guy with a level 100, 99 speed gengar that has incredible stats and wears a focus sash that allows for 1HP explosion attacks
really annoying

he also has a heatproof bronzong that knows toxic, confusing attacks, and has extreme defense
basically, you can't hurt it, but it needles you
so annoying