You can create a separate object for the weapon, and put it on the player hand through a point in the player sprite. The problem is the sword animation, as it won’trotate with the arm.
Here is an example of “parenting”, but in this example the little ship tower always follows the ship angle, has no custom rotation: [url]How to make an object parent to another? - #2 by Lizard-13]
One way to fix it is adding to the sword the same animations the player has, for example if the player has an animation “Walk” where its arm rotates slightly to the left and then to the right, you should add an animation for the sword, with the same name, where the sword rotates in the same way. Then you can sync the animations through events. The problem is that you have to create the animations rotating the weapon, and it has to be synced… hard work! 
Other way (for this particular case of the guy with the sword) is adding an extra point to the player, this extra point will determine the weapon angle, for example if the player has the sword in vertical position you add the “Hand” point at the hand, and the “Elbow” point under the hand. Then, in the events, after positioning the sword at the hand, you can calculate through trigonometry the angle between the elbow and the hand, and rotate the sword 
Surely other people will try to help you with more cool ideas if you give more specific needs, as you can see there are multiple ways to achieve it (but in the end it’s always about extra objects and position/rotation syncing) 