Not sure which thing you are asking about. The light at the trailing edge of the wingtip is the tail logo light that shines on the vertical tail.
The light hanging down from the flap "canoe fairing" is the landing light, as stated above.
Boeing Flown: 701,702,703;717;720;721,722;731,732,733,734,735,737,738,739;741,742,743,744,747SP;752,753;762,763;772,773.
Thats the Outboard Landing Light,present on the 737-100to500 series.The NGs dont have them mounted on the Flap track Fairing,instead its located ahead of the Air Condition bay under the Fuselage [Suseptible to FOD].
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