zTop for Windows Phone 7 is an app which provides statistics about marketplace application position. zTop shows position charts for selected category and region. It also can calculate average position across all regions and applications and shows last application jump. This is ultimate tool for each windows phone 7 developer.
and it might be showing up cause you Instaled it? or your usign a phone that waas used by a previous owner and exchanged with out a hardreset. lol
It was in my app list last week and I deleted it; I just did a hard reset yesterday and was reinstalling my apps manually and noticed it was in the list again! I'm wondering if it was piggy-backed on another app i installed, but i checked the other apps by the dev, and I don't have any of those installed