Photography is like a drug habit.... You get your first hit, and your hooked... you start off small (usually) then build up to the heavier stuff, and the heavier the stuff the more you want to use! So what was your 'gateway lens'? When and what was the lens or other bit of kit that broke your barrier and led to the reduced coffers most of us face due to this pricey hobby.
For me it was the EF-S 17-55. Before that I had a 450D and kit lens + 50 1.8 for years and could not imagine or ever conceive a situation where i would spend more than a couple of 100$ on a lens. Then i borrowed and subsequently bought the 17-55, and in doing so released the kraken. I had waited 2 years before buying it, but after that i added a 10-22, 55-250, tripod, 580ex II etc to the kit within a year... then came the L lenses....
So, for a bit of fun, what was your gateway lens/piece of kit?
([stand] My name is John, and I am an addict [/stand])
My gateway lens was the first version of the Sigma 17-70 (without "OS"), bought in January 2009. Optically it was a fantastic lens, but couldn't AF accurately or consistently. It was so much better (optically) than the ridiculous 18-55 kit lens that came with my Rebel Xsi, that I began to think I needed to get a more serious Canon camera...so I did. That Sigma lens eventually got me published in Outdoor Photographer, so far one of the biggest highlights of my photographic life (and I'm not young...young people would call me old, but I'm just middle aged!)
I sold that Sigma lens last year for the same price I paid for it new, $300. Worth every penny!
The next lens I bought, in May 2009 (after buying the 50D), is still my favorite of the lenses I own...the Canon 135 f/2L.
I recently read something which is probably widely quoted in photo gear circles..."if you buy cheap, you buy twice". This isn't always true, but I suppose it depends on just how cheap "cheap" is.