Another somewhat hyped card that died down once people realized how bad it was, Marley's Request can do good things, but is too dependent on your opponent. Basically, you get to dig through your discard pile for 2 Trainers, Supporters, or Stadiums, let your opponent choose which one you can keep, then discard the other. Letting your opponent choose what card you get is always a bad thing; it's akin to Rival almost in this sense. Granted, Marley's Request can work for you in several ways; either play it when you have only 1 Trainer in the discard (like that Luxury Ball you happily played turn 2), pick two Trainers with similar effects (POV and Felicity, or Bebe's and Luxury Ball), and things in that sense. But overall, it's best to avoid this card completely.
Modified - 3/10 (Unless you have a very specific need/use for this card, do not use it)
Limited - 8/10 (Your opponent still gets to choose, but hey, it's likely you'll only have a Trainer in your discard, since Trainers aren't the easiest to draft. Besides, loosen up, prereleases don't count for premier points)
Unlimited - 1/10 (So many better ways to get Trainers/Supporters/w/e out of the discard here)