Here are images from some 3D-printed successes, one from a couple years ago that I haven't taken out in a while, and one old find that was recently brought back from the dead.
The first few images are from a Dukane 3-inch f/2.5 projection lens adaptation. It was one of my first attempts at 3D-printed helicoids. It's bulky, a bit on the ugly side, employs a long aluminum rod to prevent the optics from rotating during focusing, and falls apart if you focus too close, but it's super light-weight and has held up quite well! The tiny optics are of the Trioplan variety. Even in the very center I wouldn't call it sharp but images respond well to post-processing (did some here) and chromatic aberrations are actually pretty well controlled. Contrast is a bit low, but I just noticed my sample has some haze in the front coating and there are some shiny tubes internally so a better sample could be improved.

You'll see this leaf down below as well. Wide open (my adaptation can use aperture discs but I never use 'em). Gentle overcast rainy-day lighting.

Uh oh, it's that time of year where lights are up! Center-ish crop. This lens can definitely be a bubbler, but I am no expert on that. If this is enough bubbliness for you I can recommend adapting one!

A through-the-bathroom-mirror self-portrait of the Dukane adaptation, with a rebellious tuft of unkempt hair on the top of yours truly's head in the background, refusing to be hidden.
The next few images are from a newly-adjusted late multi-coated Tokina-made 35mm f/2.8 in M42-mount. I got it a few years ago. It had all the makings of a great user lens and was a joy to operate. But when I first peered through the EVF it was disappointingly bad to the point that I was convinced something was definitely wrong with it so I set it on a for-parts shelf and forgot about it for a few years.
I recently took some time to try to figure out why it was such a lemon. As it turns out, the rear cell had a visibly defective/decentered retaining ring that was skewing those rear optics quite a bit. I felt the retaining ring itself was a little too small to 3D-print reliably so I whipped up and 3D-printed an entirely new rear lens cell that threads on in place of the old one. It uses a beefy (well, at least by comparison to the defective retaining ring) rear retaining cap instead of a ring.
It worked out better than I expected, which is always nice! It seems to be much more centered now, at least in the rear group...!

f/2.8 mid-focus distance - as with many retrofocus 35mm lenses I don't really care much for the clipped bokeh shapes towards the corners at these mid-range distances.

f/5.6 - ah, that's better.

f/5.6 from a different angle with some extra extension from my 3D-printed helicoid.

f/2.8 with more extra extension, where bokeh balls are less offensive