I usually prefer uptempo house/trance music.Some of my fav workout tunes are Sandstorm - Darude,Autonomy -Zedd,Infinity - Guru Josh,Sound Of Goodbye - Perpetuous Dreamer,Just Be - Tiesto,Sound Of Freedom - Bob Sinclair,Rise Up - Yves Larock,Titanium etc.
I don't really have favorites since I change my playlist every 2 weeks. I just randomly select around 5 artists and throw their entire discography on my music player and put it on shuffle when I listen to it.
But I usually prefer upbeat songs or those that are loud