handheld CO2 keg charger:
1. You often host parties, late in the evening on weekends. Your guests are so taken with your beer they're bringing their own steins. When your cylinder goes empty at midnight, you won't be lamenting your local homebrew store's hours!
2. You like your homebrew & your personal space, so you've chosen to live between major cities where both a LBHS and cylinder filling stores are distant. A CO2 cartridge injection is the easiest way to maintain a steady pour, and several charges over a single day can provide a more than humble level of carbonation.
3. You're a backpacker or recreationalist who often finds oneself miles from anything. Where anything heavier than a 3 gallon keg can't go, the handheld CO2 charger thrives!