with horizontal symmetry?
with vertical symmetry?
with 180 degrees rotation symmetry?

What are the LONGEST words in each category? (Common words are preferred.)

In addition to the problem about whether symmetry by letter is wanted or symmetry of the word (I also think it's the latter), there is the question of fonts.  There are some fonts in which K is symmetrical, and I chose to include that symmetry.  But I don't know of any fonts in which M and W are the reverse of each other, the former letter having its outer outline as a rectangle (with vertical lines at left and right) and the latter as a trapezoid (with all non-vertical lines).

But I guess this is just on a par with my sliding lower-case l.