What effect is this????

[Fly_rey]

Try CycoreFX CC Scale Wipe.

[Jason Shreve]

It seems like there’d be a few ways to do it as listed above for video, but for just a still, it’s Photoshop>single pixel (vertical) selection tool>copy>paste>stretch it out horizontally to the edge of the screen. This will be crazy easy to do with CS3.
You can also do the same thing in AE by masking a very small (1-4 pixel) section of it, pre-comp it, make the precomp 1-4 pixels wide, then scale the pre-comp up in the original composition. In my test I had to duplicate the layer a few times to fill it out, but it definitely worked well & required no 3rd party plug.
Good luck.

[Shawn Lance]

I found this 3rd party Plug-in.
https://www.digitaltrove.com/prime/effects/edgewarp.html
One of the filters in the Digital Prime collection.