The absolute best for consumers is AVG in my humble opinion and limited experience, but for developers with root access to your phone it causes too many flags to be thrown.

https://market.android.com/details?id=com.antivirus&feature=search_result

For most users they will find Lookout Mobile Security easier to use with less configuration

https://market.android.com/details?id=com.lookout&feature=search_result