I have a very-well-traveled friend (over 125 nations) who wraps her entire checked suitcase with ugly gray duct tape. A separate strip of duct tape covers the entire zipper.

If security wants to inspect the suitcase, they can pull the duct tape off the zipper, do their inspection and then (maybe) put the tape back. If they don't inspect the suitcase, it remains completely wrapped.

My friend carries a roll of tape, so she can seal the suitcase at the end of every hotel stay.

It's kind of the "ghetto" version of plastic-wrapped suitcases, ugly as sin and extremely easy to spot at baggage claim