Some cards work well on their own, but work especially well with certain others.
For example: Cyber Dragon and Caius the Shadow Monarch.
People have a tendancy to hold both of these cards in their hand together, instead of playing them separately.
Which isnt so bad an idea, since Cyber Dragon wont be fielded if you do have something on your field, and Caius simply adds to that contingency plan.
What about other examples?
Giant Trunade, the Dark Creator, and Dark Armed Dragon come to mind.
So does Battle Fader and Raiza.
Holding some cards in your hand as a contingency plan isnt such a bad idea.
Any other examples people care to share? Comboes that can be held entirely in your hand and serve as a possible backup plan.