The future of Pop music.
It wasn't until her 2009 release "Bad Romance" that I actually paid attention to the music she was making. Her random outfits, videos and performance were all just headline grabbing (I thought)... and they worked. But "Bad Romance" caught my attention for the simplest of reasons - It's a REALLY good Pop track!
If scientists worked out the formula for the best Pop music song that could be created, I believe that they would come up with something 99% similar to "Bad Romance". For me, it is easily the best Pop song of the last 10 (maybe more) years!
She has managed to make the sea of female Pop artists interesting. There are a few more (such as Lily Allen, Amy Winehouse and Pixie Lott) that have also grabbed my attention, but Lady Gaga, for me, is standing head, shoulders, chest, hips and knees above them all.