U2 had a whole mini-catalog of songs prior to recording their debut LP Boy, and after that they always wrote far more tunes than could fit on any one album. Some of these songs were relegated to B-sides, while others were merely played live a handful of times. For every forgettable song like “Womanfish,” there’s a brilliant one like “North and South of the River” or “Salome.” Here’s a guide to 20 of the best obscure songs from the Irish quartet.