Introduced in 1984 by Tony Magelica's Mag Instruments company, this light has been hailed (by Fortune & Money magazines, plus American Style, a book depicting classic American product designs) as an example of outstanding engineering design. You've likely seen one, but if you've never used a Mini Maglite, you may be unaware of its many clever features:

cam-driven beam, changing from off to floodlight to an intense (2200 candlepower) spot with a turn of the head patented candle-mode feature for convenient, hands-free light high-grade O-rings at each opening, ensuring resistance to water & shock anodized finish inside & out, for optimum corrosion resistance patented, self-cleaning switch that virtually eliminates oxidation low-resistance circuitry, for more efficient battery use precision-machined from the finest aircraft aluminum diamond-knurled barrel for firm gripping spare lamp housing in the tailcap unbreakable Lexan lens lanyard attachment

All this in under 6 inches (15cm) of length, weighing under 4 ounces (114g). The Mini Maglite has many imitators, but nothing comes close to the original. And you can buy one, including two high quality alkaline batteries, spare bulb, and a carry holster, for around $12. It's hard to imagine a better incandescent travel flashlight; were it not for the advent of vastly superior LED designs, this would still be the perfect choice.