I can't think of a card trick that has ever left me speechless.
I have found that, as with anything in magic, it's more the presentation than the method that makes a trick a 'miracle'. Example - according to the book The Berglas Effect, the Glide is one of the only card sleights David Berglas really used. Uses? I'm not sure how much Berglas is performing these days. Regardless - A man who essentially has a genre of card tricks named after him used one of the most basic sleights available for most of his career. He also talks about a coin vanish he would do that would get extraordinary results from the audience due to the presentation that was just a simply gimmicked method but the presentation built it up.
To that end, one of the 'tricks' I've done that gets some of the best reactions isn't even really anything. I don't even remember where I learned it, but it wasn't a magic source it was something about math. Anyway - name any two card values. Not the suit, just the value. Then spread a deck face up and look through the deck - you'll find those two values either next to each other, or with one card between them. That sounds very simple and you're literally not doing anything, right? But if you build it up it can get stupid big reactions.
If you want to get into sleights, though, Tony Chang is an excellent source of good card magic. It will be challenging for most people but his plots are excellent and thought through from the audience's perspective.