kazaa and imesh are one of the most malware and spyware injectors of the gnutella/P2P program family.
limewire, lemonwire, bearshare, zultrax, phex, frostwire, shareaza, kiwi alpha, crazaa, mammoth beta, and morpheus are not so bad compared above stated.
cabos is the most gentle for me though still a gnutella/p2p program and innocently carries deadly parasites if the other parties, in where you are getting the file, are infected or unclean.