I think lots of people would deny being manipulative because it's not a nice attribute but the truth is that a lot of us do it. Obviously, we want things our way, so what we often do is manipulate the people around us to get what we want. Most of the time, we don't even realize we're doing it.
For example, have you ever played dumb so that your significant other will do something for you? "Oh, I don't know how to mow the lawn, cook dinner, drive, etc, etc." While these examples seem harmless, in the long run, it can take a toll on your relationship. Instead of playing down your own ability to do certain things, it's just better to ask. Honesty is always the best policy.
Lastly, the greatest manipulation of them all... fake tears. Oh boy, it's so easy to get your way when you burst out the tears because he just can't stand seeing you crying and he can't say no to the tears. Again, when you fake cry, it's dishonest and it's not fair, you don't even give him a fighting chance. Instead, use your words, use your logic. If reason can't win your arguement, then it's not one to be won. Don't fake it.