What are some popular songs to sing? (please answer 10 points!)?

Just wondering what would some popular songs to sing. Because I have a youtube channel and I'm a little stuck on ideas. I really like artists like Taylor Swift, Kelly Clarkson, Lady Gaga, Adele, and Miley Cyrus. And I also like a few songs by Justin Bieber. So anything similar would be great :) And I also like Christina Perri, and Sara Barielles. And I'm looking for a song, that would be great sounding with two people singin it at the same time, while playing guitar. Because for my next video I'm having one of my friends play guitar and sing with me. And I also love Bruno Mars, and Jessie J :) So anything fairly easy to play would be awesome :) I was thinking of maybe doing "Pray" by- Justin Bieber, so yeah um NOTHING RUDE PLEASE :) Thanks :) And we're both girls if that helps :) Thanks in advance :)