When I sold my starting Sidewinder and bought my first Cobra Mk III I thought I was done with that little ship forever. Not true! It turns out I have found several uses for the little bugger and now own a few. Here are the variants I still employ from time to time:
The Bookmark: Since the game doesn’t allow for custom bookmarking of systems you can always buy a Sidewinder and leave it there to easily find a system again. 32,000 per marker.
The Fetcher: Since I am moving my base of operations to Raferty’s Mobius, and my ships are spread all over the place, I created a special sidewinder to go get them and bring them to a single location. Get the best FSD, a few fuel tanks, a cheap fuel scoop, and you can get to the system you want to retrieve your stored ship from pretty fast. It has over 20 LY range and when you get there you just strip and sell it, jumping into your stored ship ready to relocate.
The Suicide Machine: Too many people after your hide? Price on your head? Easy-peazy! Take the time-honored route of faking your own death. This is still theoretical but it seems to me you can clear a lot of annoying bounty accumulation buy storing your ship, buying a sidewinder, pulling out of the station and self-destructing.
The Sidewinder, still a versitile option--in a worthless sort of way.