Here are some suggestons:
Find out what type of batteries are readily available from his unit, when he is actually in Iraq, and source lights with that battery type(es).
(Unless of course, that you plan to give him a huge supply of batteries for his own personal use).
As much as I love modified and custom lights, stick to lights from big manufacturers that sell lights to Law Enforcement and Military. The last thing you need is a custom or modified light to fail, because it did not go through a billion tests to check the worthiness of the light.
What is his function? Will he need high powered lights to see hundreds of feet away, or low power lights to use for covert ops, say reading a map?
So, your answers will determin what type of lights that get recommended.
That said, regardless of his needs, the one light that I would recommend, would be an ARC AAA CYAN (or PEAK Matterhorn AAA Lug Style) for in his pocket or more preferably, around his neck, on his dog tags. Around his neck, he never has to remember it, he never uses it for normal opertions (that way the battery stays full until he really needs to use it).
I would also search out Lithium AAA batteries to send with him, or optionally Duracell ULTRA AAA's (I use only Rayovac AAA's, but reading some posts here, the Duracell Ultras seem to have a slight edge over any other battery, except the Lithiums).
Dont forget extra bulbs if you are selecting incandecents.
Oh, another note, we all love LEDs here, but remember that for long throw, Incandecents still are the way to go.