Describe a useful object you own

The object I'd pick is a fairly old bicycle, nothing special to look at, slightly rusted in places, that I've had for about six years now, since a friend was moving abroad and more or less gave it to me rather than deal with selling it. I use it most days, honestly, for getting to work when the weather allows, which in practice means most of the year — it's maybe a twenty-minute ride, roughly the same as the bus but without the standing around waiting for one, and considerably cheaper over time, which matters more than I'd like to admit. Beyond commuting, I've started using it on weekends too, just riding out somewhere with no particular destination, which has become a bit of a way to think through problems, oddly enough — there's something about the repetitive motion that seems to loosen up whatever I've been stuck on mentally. Why it's useful to me goes a bit beyond the practical transport angle, though that's obviously the main thing; it's become one of the few parts of my day that's reliably mine, no phone, nobody expecting anything from me for those twenty minutes, which is a kind of usefulness that's harder to put into words than 'it gets me to work'. I've had two other bikes stolen over the years, so I've become slightly paranoid about locking this one properly, which tells you something about how much I'd actually miss it.