One issue that will always hold a place in my heart would have to be Amazing Spiderman #351. It's the first issue that Mark Bagley came on as full
time artist for the series after Erik Larsen went and helped form Image. It also has a really good storyline with the Tri Sentinal and an apperance
by Nova, but moreover it was the first issue I payed for with my own money!
That's back when comics still cost a dollar!