ABSOLutely perfect *badum tss*

Your pun already made this the best. Umm Let me see, Smogen or whatever that is called useally has the best builds for Pokémon let me just link you it ^^! http://www.smogon.com/bw/Pokémon/absol

 

I would egg move Play Rough on it at least. You can do this by breeding a male Mawile that has the move with a female Absol.

 

I normally like to IV breed for a male Smeargle and use that for breeding egg moves while passing down IVs; also females can pass down egg moves.
A shame Superpower and Knock Off are transfer only moves; Superpower gives Absol Dark/Fighting coverage and Knock Off got a major boost this gen (inflicting more damage when the user has an item). You could run a Naive or Naughty nature with Fire Blast to catch things like Ferrothorn and Skarmory off guard; thanks to its Mega its Special Attack got buffed up and since you are going for a 6 IV'ed anyways.
Swords Dance is really nice to use too; especially with Mega Absol as it will not be Taunted or Will-o-Wisped and Sucker Punch is also lovely due to priority (more so with regular Absol due to mediocre Speed) However, I'm not sure if M. Absol needs SP that badly.
Play Rough is a nice move to have; gives Absol some decent Dark/Fairy coverage (things like Klefki resist that coverage) for at least neutral damage and Night Slash can also be used for a main Dark STAB; granted if its regular Super Luck Absol crits are lovely to have.
Hope this helped a bit.

 

Smeargle has only one restriction really; it can only breed with Pokémon in the Field group but thanks to Sketch, Smeargle is capable of learning any move and passing them down (i.e. giving a Scraggy Dragon Dance, Ice Punch and Drain Punch). Ditto is a universal breeder but is unable to pass down egg moves unless the Pokémon it's breeding with has egg moves.

 

It's really easy to keep the IVs and nature. Give the parent with the Adamant nature an Everstone to ensure that it is passed down to all the offspring, and give a Destiny knot to the other to ensure that 5 IVs from either parent are passed down to all the offspring. If both parents have 6 IVs, then the offspring will have at least 5 IVs and that's very good.

For an egg move, just make sure that one of the parents has it in their moveset, and for shiny, have one of the parents form a different language game.

This is why going for IVs and Shiny at the same time can be really hard.

My view on movesets is a bit off what other people think, so this might not go down well.
Play Rough looks like the best egg move you'll want for Absol, so combine that with STAB Sucker Punch or Night Slash, Swords Dance or Hone Claws, and finish it off with Psycho Cut or Zen Headbutt (also an egg move). Just keep this Pokémon away from steel types.

Alternatively you could go for Hone Claws, Fire Blast, Sucker Punch and Play Rough. I don't do mixed sets but if you go with this you might have a serious threat on your team.

 

@Tate- Steel types are no longer resisted by Dark types moves so you'll at least do neutral damage to them (apart from things like Lucario).
@Astral- In order for Smeargle to "learn" a move, you'll need to get into a double battle (I like to use Le Nah in Lumiose City) and granted the Pokémon you want to Sketch the move outspeeds Smeargle can use the move so that Smeargle can use Sketch and get that move. And if you have a male Absol, keep using that Ditto until you get a female 6 IV'd Absol. And then you can go for a 6 IV'd male Smeargle, breed with that 6 IV'd Absol until you get another 6 IV'd Absol (with Play Rough). And then use that Absol to breed with that Ditto.