The humanoid robot iCub is currently equipped with an array of capacitive sensors that provide pressure information throughout the body of the robot. Even though for some applications this type of data is sufficient, it is not always the case for the fingertips of the robot. In particular, the current sensors do not provide enough information for performing agile manipulation, where both intensity and direction of the exerted force on the fingertips are relevant for the proper execution of the task. In this paper, we present a single 3-Axis small magnetic sensor module and we show its effectiveness when integrated into the fingertips of the iCub. The sensor module is derived from uSkin, presented in previous works from our laboratory. Replaceable fingertips were designed, built and integrated via software into the low level communication network of the robot, providing fast 3D information about the contact between the fingertips and objects. Additionally, we present two experiments demonstrating tasks that would not be possible to perform with the current fingertip sensors.