For years, Kodachrome "II" (Later "25") was the standard by which all transparency film (whether color additive or subtractive) was judged. Electronic Flashes were rated in terms of guide numbers based on "KII" (The large Honeywell Stronobars were rated @ 80 with KII, a bit optimistic, though). It was extremely fine grained, and far more stable than other types of transparencies. Kodachrome transparencies from the 1940's are routinely available for view on a number of web sites. Their color is still stunning and amazingly well stabilized.
I used it for years for scenics, especially for slide presentations. It had a slight warm cast to it, much better than the blue-biased Ektachrome, or Fuji's green-biased chrome films. Fall colors with KII was always well received. Kodachrome 64 had a definite red-bias, and later on Kodachrome 200 was a bit too grainy for my tastes.
I also shot a lot of Panatomic X when I needed very fine grain, and I could use a tripod and very small apertures. The T-Max films, while having finer grain with tabular technology, just never had the pop of Panatomic X.
While the native ISO on many cameras is bottomed out @ 100, you can still manipulate the exposure to get an effective EI of around 25. I've gotten some very decent results.