The little triangle in the tooltip

Juan Diego Rodríguez is exploring four techniques to create The little triangle in the tooltip:

• clever borde (the border property of the tooltip is used for the triangle and cannot be used for anything else, but the technique is simple)
• rotated square (does not work completely in Safari for me)
• trimming the square with clip-path (versatile and usable even at the far ends of the tooltip)
• border-image and clip-path (apply the triangle without using pseudo-elements)