There are a few pieces I've picked up that are stalwarts that join me on every trip. A few other pieces are variable. I would also say that a couple items represented a painful expenditure, but have proven well worth it. I've attached a 1-10 rating for each piece. 10 represents a piece I value most and would buy again and again.
Shelters:
Nemo Equipment GoGo LE: My go-to for moderate luxury but superb weatherproofness:
http://www.nemoequipment.com/product/?p=Gogo+LE (9)
MSR AC Bivy for ultralight rides:
http://www.cascadedesigns.com/msr/tents/essential-series/acbivy/product (9)
Terra Nova Laser Comp 1, for multi-day rides in potentially foul weather, but not a great hot weather desert tent:
http://www.terra-nova.co.uk/tents-and-spares/all-tents/laser-competition-1-tent/ (full on 10)
Bags (These were painful purchases)
Sea to Summit Spark Sp1. Used for summer and ultra racing:
http://www.seatosummit.com/product/?item=Spark+Sp+I (9)
Sea to Summit Spark SpII. My primary bag:
http://www.seatosummit.com/product/?item=Spark+Sp+II&o1=0&o2=0&o3=062RL (10)
Mountain Hardware Phantom 32 for all cold weather/expeditiony trips:
http://www.mountainhardwear.com/mens-phantom-32-regular-OU8486.html (8)
Pads:
This is the only pad I'll ever use - ever:
http://www.seatosummit.com/product/?item=UltraLight+Mat (Full on 10)
Or the insulated version for cold rides, which I also love dearly. Best pads - ever.
Stove:
I'll use an MSR Windboiler for longer multi days in cool climates with lots of boiling. (10)
MSR MicroRocket for most other trips(9)
Clikstand Alcohol stove for light overnighters (8)
Filter:
MSR Hyperflow (8) or Steripen for clear water areas (10)
Headlamp:
Black Diamond - which ever is the latest and greatest. (9)
Other things I love having:
Eddie Bauer/First Ascent Down Shirt. (even in summer if temps get down in the 40s) (10)
Loksacks of various sizes for tools, trash, food. They seal in odors better than anything - no critters. (10)
MSR Titan titanium cup. The only cup I use for cooking, drinking, etc (10) The only substitute for me is the MSR Titan Kettle for more volume.
Sea to Summit Ti Spoon, long (10) Mine has been with me on three continents.
Good To-Go dehydrated food. (10)
Epic Bars (10)
Sea to Summit pillow. Perhaps my absolute favorite piece of gear:
http://www.seatosummit.com/product/?item=Aeros+Pillow+Ultra+Light+&o1=0&o2=0&o3=574-48 (full on 10)
PackTowels. The Personal towels are my favorite. I carry two or three:
http://www.cascadedesigns.com/packtowl (10)
Those are items that ALWAYS join me on trips. I've started using somewhat the same gear on the moto, but not quite the uber light stuff as motorcycle travel kills gear.