I've bought a ton of stuff since Sept '10 and of all my items, I would only replace the following with the exact same item if it got lost/broken/stolen without researching possible alternatives first:
Halcyon Harness - because I love the hardware it comes with
Halcyon weighted STA - great implementation for weight and excellent quality
Halcyon shoulder pads - I really need these when I have just a t-shirt or no shirt on. They are the best shoulder pads I've tried (also tried hollis and oxycheq)
Hollis SS Backplate - Very adjustable since it has 3 holes on top and a slit on the bottom, beautiful finish
Hollis Backpad - high quality "pad" (just thick semi-soft cordura + pocket) that keeps the cold steel off my bare skin in the summer, holds stuff like a lift bag or smb, and will prevent the wing nuts from tearing my drysuit
Oxycheq 30# Mach V Singles Wing - I love the design, very streamlined compared to other brand's wings, three holes on top and bottom for mounting adjustments and very good quality
Hollis C45 Doubles wing - high quality, even has the cordura brand tag on it showing they don't skimp on quality due to 'royalties', also has three holes on top and bottom for adjustments
Hollis F-1 Fins - For me they are the perfect weight, feel/comfort, and look.
Atomic Frameless Mask - comfort, fit, low profile, no color tint from the glass
Divesoft Trimix analyzer - compact, works great, OLED screen, cool programs like gas mix planner, teledyne R-17D O2 sensor is cheap, never needs a He sensor
Pinnacle Elastiprene Merino lined 5mm wetsuit - love the quality, fit and comfort. Keeps me nice and warm. They didn't spare any expense in the stitching patterns or kevlar padding.