Panatomic X...ASA then ISO was 32...very fine-grained 35mm with traditional grain structure...T-Max 100 is similar in granularity, but with newer emulsion technology. Ehhhh.... I didn't like it, shot only a few rolls of it.
I shot a fair number of Kodachrome 25 color slide rolls...immensely disliked it...crappy shots due to BLURRED motion on all types of shots, due to the pathetically low film speed of ASA/ISO 25...wind-motion, subject motion, HUGE problems with a film speed of 25.
Kodachrome 64 on the other hand, I shot a ton of, and yes, the ASA/ISO of 64 was not the best...I typically rated it at an Exposure Index (also called E.I.) of 80, and shot it for multiple years, from 1981-1991.
Slow-speed films of 25 to 64 are marginal for any kind of action, except in very bright lighting and with fast-aperture lenses. But they are REALLY handy for classic, pro-level studio flash type shooting, where the low film speed pairs up absolutely splendidly with high-powered flash units like the Speedotron 1,600 Watt-second and 2,400 Watt-second power supplies and two or three or four or even five flash units attached to the power supply, and large amounts of flash power being divided among the connected flash units.
A 2,400 Watt-second Black Line pack with six flash heads can easily allow you to channel 400 "real", not-inflated-like-Alien-Bee, Watt-seconds of power through each flash head, so using a low-speed film of 25 or 64 ASA/ISO was pretty commonly a "good thing" back in the day. We're seeing the same thing now in high-end Nikon cameras that offer lower and lower native ISO levels to their sensors, as well as "Minus ISO" setting capability...at times it's actually advantageous to have the lowest possible film/sensor speed possible.
Long exposures are perfect for slow-speed films! Wanna' shoot some 10-second exposures? Low-speed film can be helpful!