Thanks to its multi-wavelength instruments and re-pointing capabilities, the Swift satellite is a formidable observatory for rapidly transient sources. Here I will show that Swift high-energy instruments (XRT and BAT) are also providing us with a gorgeous wealth of serendipitous data. On the one hand, thanks to the very low background level and its excellent imaging performance, the XRT data (0.3-10.0 keV) are very well suited for the study of low surface brightness sources, as galaxy clusters. On the other hand BAT, while chasing for new GRBs, is performing the most sensitive all-sky survey in the hard X-ray domain (15-150 keV). In this talk I will first describe, from an observational point of view, current status and results of BAT AGN and XRT cluster surveys. Then I will focus on the cosmic X-ray background measurement performed in the 2-150 keV energy band.