smwddio!
In 30 years time, when my brain cells are winking out one by one, & I’ve forgotten all the Welsh I ever knew, smwddio will remain in my memory because it sounds exactly like what it means.
And obligingly, what have the lovely Welsh people named that item of clothing that can never be worn straight from the clothes line, but always needs a good smwddio first?
Crys!
Dw i’n smwddio crys.
It’s the perfect sentence.
(And I don’t even like ironing.)
Chwystrellu, to inject, to spray. The second meaning sounds quite onomatopoeic to me.
More often than not this list seems to be chosen by how the words sound and not by meaning which I think is brilliant. Some that I love …
Fwyfwy
Ledled
Igam-ogam
Sboncen
Llyfrgell
Ffrwchnedd
Môr-forwyn
And thousands more probably. I love the sound of Cymraeg.
Llwybr Cyhoeddus!
Dad taught us that on a long walk and we could say it perfectly by the end !
Ah yes, the quaint Welsh village of Llwybr Cyhoeddus 
Popty ping for microwave oven. (Well, it’s half Welsh.) I haven’t got one which is such a shame - I don’t get to use popty ping very often.
Twmplenni - dumplings, which I discovered whilst reading Mr Cadno Campus (Fantastic Mr Fox). Love Roald Dahl 
My favourite word is Pili-pala. meaning butterfly.
Some of my favourites - Is Cymraeg more onomatopoeic than other languages or am I imagining that? Or is it just because it’s impossible to avoid emphatic enunciation when you’re dealing with “ll” and “ch” and “dd”
breuddwydio - to dream
camgymeriad - mistake
rhatach - cheaper
gwylltio - to infuriate (to make wild!)
moethus - luxurious
Mine is igam-ogam - zig-zag. It’s such fun to say.
There are so many that appeal to me, it is very difficult to choose. One particular favorite though is the phrase “canu yn aml”. The first time I heard it I thought it sounded like “candy apple” and that thought has delighted me ever since.
Well, igam-ogam has reminded me of “ling-di-long” or “linc-di-lonc” “leisurely” or “slowly” which is the best way of doing anything except perhaps trying to get served in a crowded bar…
Any word ending in …og. OK, I’m easily pleased.
Also one I heard on Post Cyntaf (Radio Cymru) today, so it must be genuine:
Hoofero
og =auc in old welsh. Always wondered about Ogmore, was it ever Aucmor?. What about Aukland?
I also kind of like archfarchnad… it has a kind of “crunchy” sound to it.
Yes, almost Klingon.
Haha, yes! 'arghvarghnaD
When I tried that joke on the forum it died on its feet, much like a Kravdurgh’ch on the plains of Argyfwnyg on Seti Alpha 8
For the sound of the words, I like geiriadur and cyfrifiadur.
I also really like saying “ar hyn o bryd” as part of the lessons, for some reason it makes me feel particularly Welsh.
For memories of bwtcamp - nyddu, nawrte, go-iawn!
There are so many, but I think sigl-i-gwt and bilidowcar (wagtail and cormorant) are always pretty high in my list.