This thread (predictably) brings out certain types to do their thing.
Holy Water is available in most Catholic Churches. It is usually found in an urn, with a spigot, out in the entryway.
Feel free to go get some, yes, even you respectful skeptics--the key word being "respectful"--bring a water bottle and fill it up. The Holy Water in your bottle is a sacramental.
It has a trace of Blessed salt dissolved in it--and it is a physical embodiment of the Blessing imparted by the Priest.
Consider it a curiosity, if you like, you don't have to show it any extraordinary veneration--but again, don't do anything overtly DIS-respectful with it.
While you are there, consider doing something, just out of respect--even respect for the unknown or of possibilities in which you do not personally believe, go a little deeper into the church, even the top of the center aisle is fine, and bow toward the Altar--bow and if you feel so inclined, ask a God who may or may not exist to make Himself known to you, let Him know that that if He does exist that you would want to know.
Then go about your life, maybe with an openness toward the unexpected.
If God wants to let you know that He exists, you'll know it.