Unfortunately there are many cards in OverPower that are ineffective in serious play.  I have said it before and I will say it again, do not let me tell you which cards you should use and which you should not.  Go ahead and try them out, but not until you have learned how to play the game well.  You will be doing yourself a favor if you avoid these cards for now.  But understanding why these cards do not work will also make you a better player as you can spot the useless cards without having to be told so.
    The main term that is used when discussing useless and useful cards is Card Advantage.  Card Advantage is the general condition of having more playable cards than your opponent this battle.  Cards that are not used often are ones that will typically result in your loss of card advantage.  Universe: Basic, Universe: Training, and Tactic: Doubleshot cards are the major types of cards in this group.  For each of these three types of cards, you are required to play 2 cards for one action.  The idea was to be able to make a high level attack or defense.  But, your opponent may only need to play 1 card, like an Avoid 1 attack, to defend this attack and is now ahead of you on cards, even if it's just one card at the moment.
    There are many Specials that fall into this pitfall as well.  Most players will look at any card and ask, "What does this card bring to my game?"  There are a few answers that will automatically put a card into a deck and too many that remove a card from ever being in a deck.  When a card has a high Venture potential or a great chance to modify card advantage then it most likely will be used.  But, if it has a low Venture potential or causes the player to lose card advantage, then it better have a powerful and unique effect that cannot be had any other way or it will not be used.