I think I've still got my 6310 somewhere, but whilst it was the most reliable phone ever, it was only every a phone, whereas todays phones are amazing tools that are at times, completely overcomplicated - unless your 5 of course.
But I wish I'd kept my first ever phone though. It was the first pocketable phone after the bricks, and cost me £2700 over 30 years ago, but trebled my business because clients could always get in touch with me. We were in a pub one day, and couldn't get served, so one of the girls borrowed the phone, and rang the barman; his comments are unprintable, but we got served soon afterwards.