ATC
[obvious from my moniker]

I like them because of the detail, impact, musicality, transparency and neutrality they give me for a relatively affordable price. Much cheaper in UK than USA. Plain looking, unassuming, world-class reference monitors.
Classic KEF:
The Kent Engineering Foundry did a lot of R&D [for real] to pioneer some top notch drivers back in the 70’s. They were using computers to help designs before it was cool. The KEF 103.3 and 104.2 stand TODAY as excellent speakers
Proac:
Gorgeous looking. Slightly coloured mid band, but musical and airy as all get out.
Sonus Faber:
Like Proac, not the most informative speakers, but no matter which model you buy, be prepared to hear MUSIC. They caress notes, and articulate them wonderfully.
Vandersteen:
very liquid, transparent and forgiving. Kind of like comfort food [as reviews suggest. They could use some midbass impact, but other than that, you can listen ALL DAY long and love them…they sound like music to me.
Acoustic Energy:
These don’t cost much. They do not give you a hint that they are giant killers. They only lack the fine resolution of the big boys, but they are absolutely brilliant for the money!
B&W 800 Signatures:
damned if I can afford them, they are absolutely beautiful and very refined.
PMC:
Very informative, and possess very deep bass. These are quite nice by any measure, save plain looking like ATC.
Totem:
Beautifully musical. The one, Arro and Hawk are my favourite models in the lineup. Outstanding value from Canada. The Hawk are wonderfully transparent and musical. You will wonder how such small speakers can sound so big.
Avalon:
These are knockout good looking, and very musical and articulate. My favourite are probably the Eidolon ceramic model, followed by the Opus. I cannot afford either…damn it.
Yamaha NS-1000m: The Beryllium mid and tweeter are amazing! They are smooth, detailed and musical. Maybe the only Japanese speaker I like…a treat to listen to.
As you can see, I like informative, musical, transparent speaker that draw you into the music with articulation, and make you listen for hours. I have not heard everything, and I know there are more. If you have a personal fave…please post, and describe it.