The Rocket's Trap
The obvious downside of this card is that it relies on a coin flip. On a tails, this card is quite quite a waste of deckspace, on a heads though it can be potentially game changing.
For this card to be effective enough to work consistently in a deck requires about a 3-4 line (i.e. a lot of deckspace, for a card that possibly won't work), which is why this card rarely sees play due to the over competitiveness of the cards in the format.
On a heads though, congratulations you've probably set your opponent back a lot. Whoever is saying this card may 'shuffle rubbish cards' the majority of the time this won't be the case. In Unlimited (almost) every card in a good deck will have a use, since decks are highly competitive and easy to get hold of. Hands rarely exceed 5 cards so reducing down to 2-3 is a great thing - very often they will follow up with an Oak or Comp Search however.
What's also good about this card is that its a trainer that can be used almost whenever you want, meaning no sitting in your hand before it gets Prof Oaked away for the waste.
Honestly though, I would rather play this card. It's an uncommon and guaranteed disruption, but its not to say the Rocket's Trap isn't good. Lass is also another good choice.
Unlimited rating for the Rocket's Trap: 6.5/10