1. Gustave Praszkiewicz: Praszkiewicz, a Polish anarchist, is often credited with constructing and using a pipe bomb in an assassination attempt on Tsar Alexander II of Russia in 1880.
2. John Brown: This radical abolitionist and revolutionary used pipe bombs, or "infernal machines" as he called them, during his fight against slavery in the 19th century in the United States.
3. The Irish Republican Brotherhood (IRB): The IRB employed pipe bombs, among other improvised explosive devices, during their campaign for Irish independence from British rule in the late 19th and early 20th centuries.
4. Filippo Brunelleschi: The Italian architect and engineer designed a pipe bomb referred to as the "infernal machine," which was utilized in 1440 to assist the Medici family in gaining power in Florence.
It's important to note that the early use of pipe bombs was mainly associated with revolutionary and anarchist movements as they sought to challenge established authorities and systems. Over time, pipe bombs have also been employed by terrorist organizations, criminals, and individuals for illicit purposes.