I use all these for different purposes.
1. Color meter, Gossen Sixticolor and Minolta Color Meter II, for checking correct color temperature and correct color correction filters required. This is particular useful for color reversal film shot;
2. Spot meter, Minolta spotmeter, for visualizing contrast of the scene. This is particular useful if you use Adams Andsel's Zone System;
3. General purpose exposure meter, Minolta flash meter IV and Sekonic L608, these meters can take incident reading as well as reflective reading. The incident reading is taken to the subject and making use of dome to reduce exposure by 2 stops, this is particular useful for reversal film and digital photography;
4. Various clamp on meters, Leica MR-4 and Pentax Meter, for integration with camera that has no built-in meters;
5. Miniature meters, like Sekonic Twinmate L-208 and Voigtlander VC-2, are non-bulky and handy for taking casual reflective measurement;
6. Spot metering and average metering for Large Format metering can be taken at the film plane by Sinar Booster 1 (to use with Minolta Flashmeter IV) and Horseman Exposure Meter 45 respectively. This is particular useful for macro-work where bellow factor can be forgotten.