I've long been a fan of Exergen's (
New this year is an antimicrobial head that is now integrated on all TAT-5000 units. The head is impregnated with silver ions that are slowly released over time. The silver ions have potent antimicrobial activity, and are effective against a broad spectrum of bacteria, fungi, and other microbes. Studies have even shown that silver ions are effective again methicillin-resistant Staphyloccus aureaus and vancomycin-resistant Enterococcus. Best of all, silver ion use has not been associated with drug resistance.