i've heard people call them emo but they're a punk band as well, but alkaline trio is great! they just released a new album. the two singles from it are blood, hair, and eyeballs and bad time, or here's the entire album if you want to listen to it.
alternatively, their most popular song is called radio, and is probably more "emo" than any of those songs. stupid kid is also pretty popular, but i'm not a big fan of that track if i'm being honest. mercy me is also a good popular one but it's more mellow.