8 or 9 years ago, I upgraded from a cheap REI synthetic insulated jacket (serviceable, but not amazing) to the Arcteryx Atom LT. Since then, I can't think of a single piece of gear that has gotten more use than my Atom. It breathes incredibly well, it's super comfortable, and I've been just at home in it on breezy summer days as in the middle of winter. The hood fits nicely over a climbing helmet, and the gusseted underarms mean I've never lacked mobility. Perhaps my favorite thing about the Atom LT is the slim, athletic cut; it doesn't add the bulk that many insulated jackets do.
Now, I own several insulated jackets in various fill-weights/cuts/styles. Probably more than I should. However, I grab the Atom LT more than any other -- whether to wear around town, as a mid-layer, or as a 'just in case' lightweight jacket while romping around the Rockies in the summer. It's the most versatile thing I own.
Sure, it's a $250 jacket. But as far as outdoor gear goes, it has been one of the best investments I've made. Not only has it held up to an incredible amount of abuse, but it has gotten far more use than most of my other gear.
Here's a few of the varied conditions it's been subject to over the years:
