The Android IM app that brought T-Mobile's network to its knees.

"One study showed that network utilization of one device increased by 1,200 percent from this one application alone. These signaling problems not only caused network overload problems that affected all T-Mobile broadband users in the area; it also ended up forcing T-Mobile's UMTS radio vendors to re-evaluate the architecture of their Radio Network Controllers to address this never-before-seen signaling issue. Ultimately, this was solved in the short term by reaching out to the developer directly to work out a means of better coding the application."