My 1st foray into MF was with a TLR. A Yashica Mat124 - what a great experience that was. It got me hooked into MF with it's amazing "feel" and *HUGE* negatives. Since i really like Minolta, i flipped when i learned Minolta made a TLR (the Autocord). I promptly sourced one and love it.
Fortunately/unfortunately i met someone who had a Mamiya RB67 Pro-S. It was "love at 1st sight"! I was immediately intrigued with it's Revolving Back (RB) and how modular the camera is. Everything from a nice selection of lenses, formats (more than just 6x7), view-finders and more!!! Also, these cameras are/were professional grade/quality through and through so image quality potential was top notch. The cameras are also reknown for durability - something important for me because i take my camera outdoors alot. And finally, the price of admission was very low - especially for the quality received.