Given the choice of what can be inserted into a word balloon intended to cover up erections, I find exclamation points to be the most amusing. They certainly draw the attention of the reader. Even better, both pieces of punctuation appear to be at more or less the same angle as the erections they are covering, based on the details around the balloons.

(Heavy Metal issue #170, September 1997 – Page 110 Aphrodisia by Serpieri)