As seen here; http://i.imgur.com/rh18nwX.png I have massive GPU spikes that I simply cannot explain. Most frames a mesh would cost 0.1ms to render, and then one frame it jumps to 5 ms.
Note that the graph is in a scene where nothing is moving, no object are added or removed.
Is this on a build or in the editor? If it is on the editor, it could be the editor and profiler GUIs redrawing. To verify that, just drag and the profiler window around over the editor window and see if the pattern changes.