Welcome Kit!
Don't forget the HID's! (as Empath said above)
There are 2 great state-of-the-art lighting technologies entering the flashlight realm these days. One, as mentioned in the great examples above, is the LED lighting.
The other is from a light source like those on the high-end autos and is termed "High Intensity Discharge" lighting (a.k.a. "HID" and pronounced by just saying the names of the letters).
So if I were to recommend only 2 lights that are state of the art I'd have to recommend that you choose 1 from the LED category, and 1 from the HID category.
The problem here is that the HID lights are incredibly expensive (min about $400) so you might be stuck just showing the light from pics in the powerpoint presentation. If that fits with the assignment, then surf on over to the HID forum and also check out a great set of pages compiled by members Kenshiro and Mr. Ted Bear on their
Superlight Shootout. They've spent a gazillion hours compiling that info, and with loads of pics of the lights and their beams.
Aside from this, there are plenty of state-of-the art filament flashlights that should be talked about. For example, it's no easy feat to keep a 500-lumen bulb (such as in Surefire's M6 or 10X) from frying its internals. But if you can only choose 2 lights I suppose it's probably going to be sufficient to have an LED and an HID.
[edit] Note that my suggestions only focus on the light emitter. The other parts of the flashlight's technology are changing rapidly too, and those might be what you want to consider too. The A2 as mentioned in the other posts is indeed a good example that combines an advanced (a) emitter(has 2 types too), (b) power source, and (c) regulation circuitry.
[another edit] You might want to check out
Don Klipstein's website for how stuff works. I've found no better for HID. There's also LED info and lots of other stuff I haven't even looked through yet. I also believe he's a member here, though I don't happen to know his username. As for LED's, you gotta head to
Craig's site for some fantastic diagrams & descriptions in the FAQ section about how LED's work. There are lots of other member's sites that are great too.
