Out of my small collection;
Best modern folder opening; my Spyderco Manix FG, a solid, reassuring *THWACK!*
Best modern closing; Spyderco Pacific Salt, a solid "klak" that you can hear and feel
Worst modern folder opening and closing; Byrd Wings, don't get me wrong, it's a great knife, versatile, solidly built, and a great way to compactly carry both a SE and PE in an absolute minimum of pocket space, it's liner locks just have no *oomph* to them, a quiet, halfhearted "snik" on opening, and a near silent "tak" on closing
Best Traditional opening and closing (slipjoint); Victorinox SwissChamp, it has a brilliantly crisp opening click and a strong closing snap, they have a crisper walk-and-talk than my more expensive Case and Boker slippies (Case Trapper, Med. Stockman, and Peanut, Boker Whittler)
Best Traditional locking knife; Buck 110, crisp opening click, and a very unique closing Klakk