generally pen drive
it does annoy me when people just call it a USB without being more discriptive
you mean no one calls it a USB Mass Storage Device
Yeah, when people just say "USB" that tells me nothing. There are hundreds of thousands of USB devices out there. For cameras, cell phones, printers, hard drives, media card readers, graphing calculators, scanners, floppy readers, mice, keyboards - many, many things that are "USB". USB Mass Storage Device is a bit better, but my camera shows up as a USB Mass Storage Device when I plug it in, because it's connected by USB and it's got an SD card which is a Mass Storage Device.
USB-key because I keep it on the key chain.
I see lots of people who wear them on a lanyard. The dad of one of my friends calls it "Geek bling" when you wear a flash drive around your neck.