It takes just a peek at the online store Condomania to appreciate the variety of condoms out there.
Flavors such as island punch, banana split and bubble gum. Vibrating condom rings with batteries that last up to 20 minutes. Glow-in-the-dark condoms promising "30 minutes of glowing fun."
And under the category "Celebrity Condoms," there is the "Obama Condoms Stimulus Package," each condom embossed with an image of the president giving two thumbs up.
But even if that presidential seal of approval were real, it would not overcome a chronic and serious public health obstacle: Most men do not like condoms.
Now, an influential player in global health, the Bill and Melinda Gates Foundation, is getting into the game. The foundation just finished collecting applications for what it calls a Grand Challenge: to develop "a next-generation condom that significantly preserves or enhances pleasure."
The goal is to address two significant problems: unintended pregnancies and sexually transmitted diseases like AIDS. Condoms cheaply and effectively prevent both, but around the world only 5 percent of men wear them and there are 2.5 million new HIV infections a year. To stem that tide, health experts say, the number of men regularly using condoms needs to double.
"Decreased sexual pleasure is typically the predominant reason for not using them," said Stephen Ward, a program officer for the Gates Foundation. "Can we actually make them more desirable? That's what we're shooting for."
More than 500 applications poured into the Gates contest, which will award winners $100,000 this fall, and up to $1 million subsequently. And in a first for a Gates challenge, Mr. Ward said, people sent samples.
"Boxes of condoms, condom accessories, condom cases that look like something else so women can be very discreet while carrying them," he said. "We received a completely stocked carrying case with condoms, lubricant and breath mints."
Condom experts -- some of whom have studied the subject for years -- have ideas of what might work and what decidedly won't.
"I don't think we've seen the condom that knocks the socks off for everybody," said Ron Frezieres, vice president of research and evaluation at the California Family Health Council, a longtime tester of condoms for industry, government and nonprofit organizations.
"Guys would like it if they, first of all, don't believe they're wearing it," Mr. Frezieres continued. "And second of all, it's got to be a little better than what they're used to. We still have to find that perfect bullet."
Perfect may not be the enemy of the good in this case, but it is awfully hard to pin down.
"When I saw that Gates announcement," said Jeff Spieler, a senior technical adviser on population and reproductive health at the U.S. Agency for International Development, "I wrote and said, 'It's great that you're doing this, but I've been there before, and I hope you're going to surface something that I couldn't surface.' "
This "has been my passion for years and years," Mr. Spieler added. "I started thinking, 'Gosh, if we could develop a condom that made sex better with the condom than without ... .' If at least it didn't take sexual pleasure away, it would not be like taking a shower with a raincoat on."
At first, he recalled, his bosses said: "Hey, Jeff, be careful. We don't want Congress to come beating down on this because Jeff Spieler's trying to make sex better."
Several manufacturers have worked on more appealing condoms. Some models, like Pleasure Plus and Twisted Pleasure, designed by an Indian surgeon, Alla Venkata Krishna Reddy, whom Mr. Spieler called the "Leonardo da Vinci of condoms," addressed complaints of tightness and friction. They are roomy, ballooning, "sort of like the swirl of a Dairy Queen ice cream," Mr. Spieler said. The movement of extra material is intended to be stimulating.
Mr. Frezieres and his colleague Terri L. Walsh conducted studies involving condoms with lubricants that create a heating sensation.
Another testing quandary, Mr. Spieler said, is that "you can't compare one sex act to another sex act. You can come into a sex act having just argued and having makeup sex. You could have three days of bad sex, so you don't rate the condom you're testing very well."
That has not stopped innovation in the condom industry. There are vibrating condom rings like the Durex Play -- Ring of Bliss, said Bidia Deperthes, a senior HIV technical adviser for the U.N. Population Fund. (Mr. Spieler calls her "the condom czarina.") Some men invariably gripe about the battery life: "Bidia, 20 minutes, it's not that long." Her response: "Guys, give me a break. Fifteen minutes is already flattering you."
Ms. Deperthes, whose office features a wall of condoms, has versions packaged like lollipops, miniature chocolate milk cartons and cellophane-wrapped taffy.
And what's that pinned to her silk blouse? A brooch of batik fabric. But on the flip side of the pin is, yes, a condom. Talk about wearable art.
And perhaps the most innovative new American-made product is the Origami condom, still in clinical trials. Its inventor, Danny Resnic, said he was motivated by his own experience when "a latex condom broke and I wound up with an HIV diagnosis."
Years of experimenting led him to devise a condom with accordionlike pleats, loose to allow movement inside. Made of silicone, which is meant to feel more like skin, it "goes on in less than a second," he said, and "there's no wrong way to put it on."
Besides male condoms, which Origami calls "external condoms," the company has a female version (an "internal condom"), and the first condoms for anal sex and oral sex, Mr. Resnic said.
The Gates Foundation contest also welcomed designs for female condoms, but female condoms have historically been less popular.
In the developing world, condoms raise other issues. In some cultures, men are so resistant that women must engage in delicate "condom negotiation." And women who carry condoms might be assumed to be prostitutes.
Ms. Deperthes and Franck DeRose, executive director of the nonprofit Condom Project, use songs and dances about condoms to try to make them seem fun, and give women ways to carry condoms discreetly, including containers that look like breath mint boxes.