I, too, have or have demoed every product mentioned so far with the exception of EchoBoy (which takes a dongle, so I'm not interested). Why so many? Well, partly because every one of them has fallen down in at least one regard; maybe it lacked an important feature or was just too clumsy or time-consuming.
 
99% of the time, I'm after a basic delay rather than some carefully-crafted rhythmic effect. So my go-to delay has to be simple but still have all the essential features. So scratch Timeless 2, it can do amazing things but simple tasks aren't always straightforward. Scratch RP-Delay for the same reason. Tritik tkDelay is a favorite, but mainly because it has a couple features most delays don't have (in particular, the Reverse function) - it's not the one I reach for first, either.
 
Imperial Delay has pretty much every feature you can imagine. It's well laid-out and simple to use, but you can dive deep if you want to. Its two-stage feedback feature is unique and wonderful on leads and vocals. But I hesitate to recommend it because I feel it's overpriced.
 
So what will you find in 90% of my projects? The good ol' Sonitus Delay. It's a plain-jane wallflower next to more modern offerings, lacks some advanced features, and it still has some issues dealing with tempo changes. But it's just so quick and easy to use! Takes 5 seconds to drop it in and tweak it.
 
[EDIT] I forgot to mention an often overlooked oldie-but-goodie: Ricochet from Audio Damage. Just 49 bucks and deceptively simple. Almost the equal of the Sonitus for quick results but has additional features such as chorus in the feedback loop and separate filters and panning for each tap.

No dongle for EchoBoy in v5, Bit.

Another good and cheap Delay.
http://www.hornetplugins.com/plugins/hornet-deelay/
 

Lots of great ones here I've not heard of that I may have to check out.
 
Depending on your budget there's Bloom from fxpansion, it does some unusual tricks that I've not seen from others.
 
More Bloom
 
Steve

Fleer
No dongle for EchoBoy in v5, Bit.

Good news. Still Pace, though, and it's as much the software component as the physical dongle that I want to avoid.

PSP Echo at $29 is insane. This is my go-to delay for guitar. It's a tape echo and you can make it as clean or "analog" as you'd like. At that price it's a no brainer!

Do you think it's comparable to IK's T-RackS Echo, dlesaux?

Nomad Factory's Echoes is good for various tape/oilcan/analog echoes.  It does have sync and controls for how deep to ping pong.
 
Prior to that I used to use the Kjaerhus delay for analog/tape.  I don't know where you can find it these days, maybe VST Warehouse?
 
Another good freebie is the TAL Dub-Delay.
 
Also don't forget Guitar Rig.  It has a handful of delays, and you can use containers to layer multiple instances.

If I may be so bold as to toss something I cobbled up into the discussion: https://tonecarver.wordpress.com/delay8/
 
It's a delay plugin based on the UD-Stomp / Intellefex architecture: 8 delay lines, cascadable, with individual modulation and hipass/lopass/pan per line. Great for complex choruses, Holsdworth-type of delay effects, and can even get into the near reverb diffusion territory (see the Atmo Linger preset, for example). The GUI could use an overhaul (I don't seem to have a knack for making nice GUIs) but the engine has been pretty solid and the price is good too ... free  :) 

Thank you, Bill. I'm gonna try it out!