Unity seems to interpolate from one keyframe to another even if the frames are consecutive?! How to fix this? modify in/out tangents in all animation keys of a particular object? I need a snap behaviour for a some objects...
If you can't find a stepped tangent like in Maya, you can do a hack.
0 1 2 3 4 5 6 7 8 9
1 1 5
Top row being the time line, bottom line where to place keys. So if you were animating in y, place a key in time frame 0 at 1 y, and a keyframe in time frame 5 at one, that will make it always one till it pops at keyframe 6. I hope I explained it right. Not that experienced with animation editor in unity, but I use that in maya sometimes as a quick hack.