The Burnmaster, the Nuka-grenade, and the Zhu-Rong v418 Chinese pistol are unaffected by the perk. The guide lists these as being affected by this perk, but the weapons aren't on the form list - this is most likely an oversight by the developers. [verified]
Any flamers that are brought back by the Gary-23 glitch from Operation: Anchorage are also unaffected. The reason for this was probably because weapons from the expansion were not meant to be brought back, thus they are not affected by this perk. [verified]
Fallout: New Vegas
“With the Pyromaniac perk, you do +50% damage with fire-based weapons, like the Flamer and Shishkebab.”— In-game description
With the Pyromaniac perk, you do +50% damage with fire-based weapons, like the flamer and Shishkebab.
While fire-based, ammunition is not affected by the Pyromaniac perk.[verified]
Even though weapons like the Shishekebab are affected by the Pyromaniac perk, the additional burning damage is not boosted.[verified]
While this perk requires an Explosives skill of 60 to be unlocked, the only explosive items affected by the perk are the incendiary grenade and the fire bomb. This was confirmed by Joshua Sawyer to be unintentional; the perk was meant to be dependent on the Energy Weapons skill, which governs most ranged fire-based weaponry.