The new developer guidelines are out for the Windows Mobile Marketplace for Mobile storefront, an applications store built by Microsoft which supports Windows Mobile 6, 6.1, and 6.5. The new guidelines set stringent approval processes for applications approval, even tougher than Apple's guideline. The positive thing about Windows Mobile is that even if apps are banned from the official Marketplace, users can download and install those apps from other storefronts and from the developers themselves.
The guidelines set limits on no pornographic content, no violence, and no gore, bloodshed, or profanity. Looks like you won't be finding any first-person shooter games in the Marketplace.
Here are the guidelines:

• Any content that contemplates harm against a person or animal.
• Any content with prolonged and/or excessive use of firearms or weapons or other content that facilitates the use of firearms or weapons
• Weapon imagery depicted in the act of harming humans or otherwise inconsistent with the Windows® Marketplace for Mobile guidelines on violence
• Sex / Nudity
• Images that are suggestive or sexual (e.g. sexually provocative touching, bondage, masturbation) or provocative images that reveal nipples, genitals, buttocks, or pubic hair.
• Any adult and/or borderline adult content (images or text).
• Content that depicts or suggests prostitution.
• Any content that depicts decapitation, blood splatter, killing, gore or cruelty
• Any content that depicts excessive violence such as repeated blows or shots inflicted upon people/creatures, violent blows to the head, guns/weapons pointed at head, impaling, exploding body parts, guns/weapons pointed toward reader/audience, depictions of fatal injuries, strangulation/choking, inflicting wounds with swords/knives
• Excessive and gratuitous amounts of blood and/or fleshy body parts, blood spurting from wounds
• Excessive Profanity

(via: WMPowerUser)