Most Important Men's Vitamin

What is THE most important vitamin for a man to take if he was only going to take one?  I have been looking for a men's vitamin that includes everything a man needs but not being male, I don't know what that is and my husband doesn't really care all that much.  I have been telling him for the last few years that he has to start taking Lycopene for his prostate but he has no clue what Lycopene is (he probably doesn't know what a prostate is either).  I set his vitamins out for him and he's good for the first day or two of taking them and then he stops.  Maybe if they tasted fruity and were chewable like the kids' vitamins, he'd remember to take them.