74LVC1G125 on the arduino wireless shield?
It could be used for a number of reasons. One use can be a more powerful driver if you need more current. Another reason can be to protect a more expensive part from ESD damage or shorts which tends to happen to an exposed I/O. It's cheaper to replace a buffer than a processor! Another reason could be to keep return paths short, reducing loop area inductance (helps with signal integrity and EMI).