How much do you want to spend and what are the criteria for a light used in mountain rescue?
Consider some of the lights used in caving. They typically will have high brighness AND power saving modes, but the big difference typically is weight - AAAs are typically not going to cut it for 10+ hours underground unless 1)you want to fill your light with mud by constantly opening to change batteries or 2)you never have enough light to see the passage you just passed.
http://www.stenlight.com/http://www.petzl.com/us/outdoor/headlam ... d-series-0There's a post here with a nice spreadsheet of lights:
http://forums.caves.org/viewtopic.php?f=2&t=14881Just be prepared for some sticker shock - a good light in caving is like good boots in mountaineering
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I have the petzl duo 14 - it's a great light but dated - the halogen option really only offers redundancy since the 14 leds are just as bright. Frankly the petzl ultra-vario, sten s7, or really anything based on a cree xml - might be a good option. These lights have options for a super long throw - the difference between seeing a problem at a distance vs wasting time to walk up on it. Of course that said, you could save a lot of money with a more standard headlight, and the a secondary handheld torch style light.