Suited Connectors
I play them as often as i can -- if it`s cheap enough. You can lose a lot of money, very quickly, if you don`t take the price of initially playing them into account. Plus, you have to commit to throwing them away if you don`t hit.
Another good time to play them is against opponents who never switch up the range of cards they play, so you know that if you play middle to low connectors and they hit (in the absence of any higher cards, of course), you`re almost certainly ahead.