OK... Limiting it to 'inexplicably cheap yet good' and only 5 (which is not easy!)
#1 Nicole Miller for Men - Keep seeing it at Marshalls, etc. for $10. Really very good.
#2 Bijan for Men - I just love this one. Some say it smells like cardamom. It's unique and always cheap.
#3 Azzaro Visit - If you like cedar / incense, there aren't many like it at this price.
#4 Z-14 - Andrew was right about this one. Always available at a low price, always good.
#5 Quorum - There's only one like it, and it's always cheap.