Not a Perfume 
Juliette Has a Gun (2010)

On my skin... Vaguely reminds me of ambergris. It's salty, rotting dead sea creature, seaweed something, with a tinge of something alive and green. Then it's musky, like faint body odor, on a sweaty day. Sometimes it even smells like mixed greens with a hint of ozone. It doesn't smell too bad on me actually. It comes and goes as if by magic.

The emperor's new clothes - I wouldn't buy a full bottle, for such a vague "scent".

This is indeed not a perfume. Perhaps the height of industry cynicism or just a hilarious placebo experiment, Not a Perfume (2010) is extremely useful to any serious perfumista or colognoisseur for one reason: this is one of several references for ambroxide, the oft-used base aromachemical for modern designer perfumes since its popularization in the same year this was launched. Almost an omen is the release of Not a Perfume, showing off the synthetic ambergris tone Francis Kurkdijan used in the previous year's Lady Vengeance (2009) all by itself, and its importance is in allowing those who often malign the "ambroxan overdose" purported to be in every major designer release to actually familiarize and recognize a variant of the note on its own. Cetalox is of course just one patented variant of ambroxide produced by Firmenich that isn't a single molecule like IFF's Ambroxan, and may differ from Mane's Orcanox, and Givaudan's Ambrofix.

Escentric Molecules did this same trick with ambroxan on Molecule 02 (2008), which is a purer representation that offers an even wider range of reactions from smelling nothing to being overwhelmed hours after application, but the point still gets across. This opens as almost nothing too, since the nose doesn't readily detect something this chemically-pure even if it isn't a single molecule like actual ambroxan, because this is meant to enhance a perfume rather than be it alone. However, within five to ten minutes, the familiar warm, slightly earthy, tad salty, and ambery vibe signature to an accurate reproduction of ambergris appears. This doesn't have the depth and complexity of real ambergris because let's be honest, the impurities found in a naturally-sourced ingredient are exactly what gives it depth, and this is just a pure single chemical in wearable dilution.
What Not a Perfume does also varies greatly upon skin chemistry, since it will literally enhance what is there already much like any chemical base note, just not as wildly as Molecule 02.

The clincher here of course is the price, since you're effectively paying full retail price for an entry-level niche brand (over $130USD at time of review) for something you can buy in pure form for much less just because it is diluted and presented as a perfume, hence the cynicism. On the plus side, you can use this as a base for a traditional eau de cologne like 4711 Echt Kölnisch Wasser (1792) if you don't mind an ambergris base, but you could also just muck around with industry aromachemicals for cheaper so it comes down to price for convenience of a pre-mix, like with alcoholic cocktails. My recommendation is just to sample Not a Perfume for an ambroxide reference, then use it to determine if the cause for your much-loathed modern designer accord is really ambroxan or something else like norlimbanol. Educational, but not really wearable, Juliette Has a Gun Not a Perfume is exactly that. Solid neutral for me because I appreciate the edification if not the absurdity of the presentation.