Both are great for cardio playlists or just "dance party" playlists! I will warn you that once you hear them, it will be ridiculously difficult for you to get them out of your head!
Rihanna - We Found Love
*I just want to put my "going out" clothes on and dance for hours every single time I hear this song! Ri-Ri is ON FIYAH right now!!
David Guetta feat. Usher
*I don't like Usher...let's be clear on that...but David Guetta is a genius for picking him for this track. It's muscial perfection and I actually enjoy hearing Usher's whining for 3:35 ;)