Four dice, added
With four dice the totals cluster tighter still. Most rolls land between 11 and 17, and all four sixes happens once in 1,296 throws.
4d6, drop the lowest
The most common way to roll D&D ability scores is four d6, throw away the lowest, and add the other three. Do it six times and you have a character. The stat roller does exactly that, all six rows at once, with the dropped die struck through.
Critical hits
A critical hit in D&D doubles the damage dice. A greatsword's 2d6 becomes 4d6, and a 3rd-level rogue's Sneak Attack doubles along with it. Set the count above and roll the big one.