Well, not backpacking gear, but certainly an outdoor object.
My Koga-Miyata World Traveller touring bike, circa 1990.
I was stationed in Germany, and had rediscovered the joy of cycling (thanks to the wonderful and bike friendly German countryside). After a month and a half field exercise, I took my unspent paychecks and bought the most expensive thing (except a car, and it was even close to that as all my previous cars were used) I had ever purchased up to that point.
That Koga-Miyata opened up the world to me in a way it had never been opened up before. Shortly after its purchase I rode my bike from Garlstedt (between Bremerhaven and Bremen) to a really cool concert. In Berlin. The 'Wall' had come down but East and West had not yet reunified. I rode my bike to the Roger Waters 'The Wall' concert at Potsdammer Platz in East Berlin (which was incredible, BTW, both musically and historically). Then rode down to Dresden, up to Leipzig, and down back into West Germany to Munich. On my own, camping along the way. I have enough stories from that one bike ride to span multiple bottles of scotch and beer halls full of laughter.
I went on to ride, generally three weeks at a time, in New Zealand's south island, Ireland, northeastern France, Holland and Scotland. All unsupported, just a buddy and I. Wonderful adventures all. After I was back in the States I even did Arizona for three weeks.
So that bike, more than anything else, shaped me into who I am today -- my world views, my desire for activity-filled adventure (instead of prepackaged, sanitized and chaperoned adventure so rife in today's world), and even helped me gain a level of maturity that had been sorely lacking up to that point.
I still have that bike. It's the one thing I don't think I'll ever let go.