An interesting episode in the history of halacha, as well as Jewish modernity, concerns the issue of whether it is permitted to shave on חול המועד hhol ha-monged. The specifics and who aligned on what side are not important to this post. What is important is that Isaaco Samuele Reggio (known as Yashar) wrote a pamphlet called Essay on Shaving מאמר התגלחת, which argued that it is permissible (see below).
Incidentally, Reggio had once gotten into a chol ha-moed related kerfuffle ten years before; in a time when synagogues had strict rules, the rules in the only synagogue in his native Gorizia did not permit people who would not wear tefillin (on chol ha-moed) to pray there. Naturally, there were two camps; wearers and non-wearers, but only wearers were permitted to pray there. The issue had existed in that community at least since 1716, with responsa and intrigue (!) on both sides. By 1824, it seems that non-wearers were tacitly permitted to pray. It so happens that on Hoshana Rabba of that year, a congregant named Abram Vita Morpurgo chose to pick a fight with Reggio and another man, the two who were praying without tefillin. It seems that a commotion was caused, and calm was restored when the two men agreed to leave.
In any case, the next year he tried to get permission from the synagogue authorities for people who were not wearing tefillin to pray within. They decided to accept a ruling from his father, Gorizia's Chief Rabbi Abram Vita (אברהם חי) Reggio. As he personally favored not wearing tefillin, it is not surprising that he permitted the synagogue to revise the rule.
In any case, the elder Reggio strongly disagreed with his son and wrote a response arguing that shaving is not permitted, cleverly titled Shaving the Essay תגלחת המאמר!
Below is a rare picture of the elder Reggio, perhaps not what one expected.