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Let me present to you, The Most Obnoxious Team Ever. This team takes absolutely forever to defeat even if you do defeat it, and is basically a team that refuses to actually ever get around to attacking you, but oh god will it hurt you.

Hippowdon@Leftovers
Impish
~ Earthquake
~ Slack Off
~ Stealth Rock
~ Roar

Meet my lead. Hippowdon leads to get the Sandstorm damage started, and is an absolute physical wall. Slack Off is a nice recovery move if I don't think a certain Pokemon poses any threat to Hippowdon, Stealth Rock is obvious for the setup on this team, and Roar lets me shuffle around Pokemon to take them through said Stealth Rock (and other entry hazards). Earthquake is a good, solid attack move that gets STAB and covers a whole lot of stuff.

Skarmory@Leftovers
Impish
~ Brave Bird
~ Roost
~ Spikes
~ Whirlwind

Are you noticing a pattern yet? Skarmory is another absolute wall of a Pokemon, albeit one with different coverage than Hippowdon. A very similar moveset - Spikes as another entry hazard, Whirlwind to shuffle them around, Roost for healing, and Brave Bird as a good STAB attack.

Dusknoir@Leftovers
Impish
~ Will-o-Wisp
~ Pain Split
~ Earthquake
~ Ice Punch

TWO attacking moves? Golly! Will-o-Wisp allows Dusknoir to come in and immediately cripple many physical sweepers. Pain Split is a healing move, albeit a bit unreliable especially in this team, and I might switch it for Rest. Quake and Ice Punch provide good coverage, and are a nice surprise for someone who doesn't expect Dusknoir to have anything 'useful', per se.

Forretress@Leftovers
Relaxed
~ Spikes
~ Gyro Ball
~ Rapid Spin
~ Reflect

Here's another Spiker, but with different uses than Skarmory. Reflect can go up to make the wallingness of this team even more... uh, wally; Rapid Spin is good to deal with any entry hazards that this team ends up against, since it doesn't particularly like dealing with them either. Gyro Ball, due to Forretress's abysmal speed, can do a TON of damage and is a neat little surprise.

Blissey@Leftovers
Calm
~ Wish
~ Softboiled
~ Flamethrower
~ Toxic

Wish and Softboiled ensure that Blissey will be able to heal not only itself, but the other Pokemon on my team. Toxic combined with Softboiled ensures that a Pokemon's either gonna have to switch out (and thus eat SR + Spikes damage) or eventually die, unless it's something that Blissey shouldn't be in on in the first place.

Vaporeon@Leftovers
Bold
~ Wish
~ Protect
~ Surf
~ Yawn

Wish and Protect allow Vaporeon to heal itself - or, in a pinch, other people as well, though Blissey fills this role better. Surf is a useful STAB move if I need to actually attack something directly; Yawn puts things to sleep and forces switchouts (for more SR/spikes damage).

This team is not a fast team. It takes forever to do its job, and it is incredibly frustrating to play against, but boy will it piss you off. The general strategy is to use Hippowdon + Skarmory + Forretress to get up a good setup of SR and as many Spikes as possible, and then just keep forcing switchouts. And it hurts. A lot.

Go ahead - and yeah, I realize there are some walls I didn't use (Uxie, the Regi trio, etc) but I only had room for six. And if I expect a Rapid Spinner that's what Dusknoir is for - it comes in, goes "hahahah normal attack" and eats the Rapid Spin, while hitting back with EQ, Ice Punch, or just Burning it.

Better than what? What would I replace for Uxie, for example?

Vaporeon also provides valuable sleep support with 100% accurate Yawn, has good type coverage for leaping in on Water attacks, and is very bulky.

Sandstorm is intentional; the few pokemon that take damage from it (Vaporeon and Blissey) are more than capable of taking damage. Dusknoir doesn't really like it but is rarely in for long; the other three are immune.

Yeah, but like I said, what do I replace? One of the reasons I like so many of the ones I have is that they can heal themselves easily (Hippowdon, Blissey, Vaporeon, Skarmory), and the ones that can't fill very specific roles that Uxie and Registeel can't (Dusknoir as Rapid Spin blocker, Forretress as Rapid Spinner).

Don't get me wrong if I had space I'd throw them in but there simply isn't any space for them!

Yes, but Sandstorm is also hurting the opponent, and Vaporeon and Blissey are much more well-equipped to deal with the Sandstorm damage (since, uh, both of them have healing moves!)

I knew perfectly well what I was doing when I included Hippowdon as a lead. Sandstorm is just more added damage along with Stealth Rock and Spikes.

I'm inclined to agree with Nerosan. Sandstorm is very deliberate and while Bliss and Vappy are getting hit from it, they're recovering the damage with Leftovers, which is what I assume the point of Leftovers was. And if excess damage starts overwhelming them, then they've got Wish to heal themselves up nicely, as well. Sandstorm teams don't have to be wholly Steel/Rock/Ground.

Also yes, technically Blissey can't learn Wish except from an event, but I think things like that are stupid. If you really have a problem with Blissey having Wish on it, switch it out to something else like Aromatherapy (which makes Vaporeon even more necessary, IMO.)