I like the BYOC Shredder. I just got a new enclosure, some knobs, and a couple components from Mammoth Electronics. Gonna try a mod I've heard great things about, then rehouse it in a fresh translucent red box. Gonna be cool.
The two that seem to keep returning to my board are a Tonebender MkII and a Madbean Kingslayer. The Tonebender would be permanent, but it's too noisey on a power supply and I hate changing batteries. Got a Lunar Module on the way that I'm hoping will replace it for good. The Kingslayer (Klon variant) just seems to have the perfect eq for my rig - I actually like it quite a bit for heavy distortion (contrary to conventional wisdom on Klons) but it also does the edge of breakup thing really well.
In terms of kits, the BYOC Flanger just flays the competition. It's Flan-tastic.
In terms of my own noodling around, I breadboarded a MK1 Tonebender from a Gary Hurst schematic that just destroyed. It was so good I was plugging my breadboard directly into the amp for a couple months. Crazy seeing all these wires and components sitting on the top of the head stark naked.
I eventually had to use components for other builds, old Mustard caps and carbon comps and oddball parts. And then I got a Skreddy LM Deluxe which satisfied my Fuzz jones.
I built one up from the same schematic and it just sounded yuk. Maybe I just had correct magic combination of parts and transistor gains. It was crazy good. I know the MK1 is notoriously finicky. I should do another one.
BSIAB and Dr.Boogey, the two is really nice sounding pedal and very versatile. My Boogey using gaussmarkov schema and slightly tweaked on tone control. I've build Diefet also but it's sounding too tight for my music now, but it's nice too.
Oh man, I've built a few. Staying on my board are BSIAB, a GGG Tubescreamer clone, and a GGG Ram's Head Muff. All incredible. The best would be difficult to choose. The BSIAB if it's measured by how often I use it. The Muff by pure classic recognizability. The Tubescreamer for raw mojo.
Not staying on my board: my own Rat clone, BYOC compressor.
I've posted this on TGP before, but here is perhaps my hardest build. A big muff (full circuit) in a Hammond 1590A enclosure:
It was a tight squeeze but I like perfboard because I can get creative with the layout. It sounds amazing.
I've also built a Tremulus Lune tremolo, two other muffs, a few overdrives that quickly left the board and got scavenged for parts (it turns out I only like muffs), a few boosts, etc. I build my own amps, too, but building pedals is way cheaper, and the payoff is much quicker.