Velvia - is my favorite multipurpose film. Incredible gamut, high color saturation. I use it for landscapes, cityscapes, architecture, nature, travel. Don't use it on people unless for special effects. It is the sharpest color slide film on the market - sharper than Provia.
100SW - warm tones, saturated. I especially like to use it for flowers.
Astia - moderate saturation, true colors, natural skin tones. Great for people, fashion, product shots.
100S - a 100SW's cousin, but without warming effect.
Fuji 64T - nice tungsten film. I like it for night city scenes.
Provia 100F - dull colors, biased towards blues. It has the finest grain (although Velvia has better resolution), and it pushes well.
I would stay away from any ISO 200 and higher slide film (tried many of them - poor colors, too much grain and contrast to my taste).