I bought some no-name rechargeable CR123s and a charger from Taiwan about 5 years ago and they still work pretty well.

I also have some Ultrafire 16340s that are pretty good, but the known voltage is 3.6V, not 3.0V. Some flashlights can handle this and output the same (or brighter) beam. Some flashlights can't handle it and it will fry them immediately. They are also a few mm longer than a CR123A, so not all flashlights can accommodate them. More info here: http://www.batteryjunction.com/uf16340.html

The Ultrafire 16340 batteries are a replacement for standard CR123A batteries in many applications. Sometimes called an RCR123A or Rechargeable CR123A, these cells may be longer than a standard CR123A. Caution must be exercised when using these cells, as they are 3.6V, not 3.0V as is a standard CR123A. The length of the cells are longer than a standard CR123A (up to 1-2 mm longer), so if you're using 2 in series be aware that this extra length will be doubled (up to 4-6 mm) and the cells will be outputting 7.2V(8.4V peak).