So, I work with some traditional materials, which are sparkly. For those that want to work with sparkles, here's some links to various things I've found or used.
Please bear in mind that I am NOT affiliated with any of these stores, brands, or anything - they're just stuff I've found over the years.
Jetpens has a VERY helpful article going over metallic and glitter pens
that they stock on their blog. It's worth a read! Wink of Stella Brush Pens
These take a bit to get used to, but overall are VERY nice to work with. If you're a fan of brush pens, these are rather nice. I personally prefer the clear pen, because you don't need to worry about color matching. Wink of Luna Brush Pens
Similarly to the Wink of Stella, these are metallic and not necessarily glittery - but they do have a nice sheen. Uni Ball Signo Sparkling Glitter Pens
I got very similar pens about 10 years ago, and they are going strong. Uni's a very good brand. Sakura Gelly Roll Pens
I've bought a few different varieties of these over the years -- while not one of my favorites (they clogged a lot), they're a well-known brand. Atyou Spica
These are made by the same company which makes Copic markers. I've not had a chance to play with them, but they seem pretty popular, and are good for scrapbooking -- which means they likely won't damage your art if used carefully.
Paints & Mediums Winsor & Newton Iridescent Medium
Winsor and Newton's iridescent medium is something you use alongside your paint. You can blend it in with pretty much any pigment you have, or layer it on top. Daniel Smith Luminescent Watercolors
I do use this brand a LOT. The luminescent colors are quite nice and some shift between multiple colors. The only downside is that the tubes sometimes separate out into gum arabic and the pigment, which can be a pain if you're not prepared for it. Yasutomo Pearlescent Colors
These are low-priced, but good for what you pay. Niji/Yasutomo has been pretty reliable with their materials, with a reasonable price. They can be used on their own, rather than an accent which is pretty convenient. Unlike other brands that are caked like this (I'm looking at you, Artist's Loft), they don't get all chalky after they've dried. Artist's Loft Pearlescent Watercolor Pan Set
These are cheap, both in cost and in quality. If you have NOTHING else and must try some sparkly paints, I guess these are okay -- but I warn you: they do get chalky and gross-looking after they dry on paper. I don't care for it, and am only linking it here if you really, really have to get it. Zig Kuretake Pearlescent Watercolor
The picture makes this look big. It's actually pretty tiny, but the color goes a very long way! Jacquard Pearl Ex Watercolor CD
This is pretty much the same exact thing as the Zig Kuretake palette -- only branded differently. Twinkling H2O's Shimmering Watercolors
These were interesting to work with. Not a favorite of mine, but they are easy to store and such, if you want your watercolors completely separate. Da Vinci Iridescent Watercolors
You can find a set of these colors
so you don't have to buy them one-by-one. I've heard good things about Da Vinci's brand, but haven't tried it. Maybe I'll pick some up the next time I'm in a store where it's carried in my area. Da Vinci Iridescent Watercolor Medium
I'm honestly not sure what the difference in this and the Winsor and Newton stuff is. It might be more finely ground, but until I've had a chance to try it, I can't say! Turner Acryl Gouache
Note: Only some of these colors are iridescent, pearlescent, or metallic. If you decide to go with this brand, please look over the color choices carefully. I've seen this brand in stores, but as I don't use gouache as I prefer more transparent colors. You can learn a bit about gouache (and how it's different from watercolor) on Wikipedia
Inks Liquitex Acrylic Inks
Liquitex makes some nice inks which are iridescent in nature, though it does not account for the entirety of their materials. Make sure to read the descriptions and color choices carefully. Dr. Ph. Martin's Iridescent Ink
I've used other things from this particular brand (such as their watercolors), and it's actually quite nice. I don't doubt that their iridescent inks will be nice for calligraphy or adding finishing touches to a piece.
J. Herbin 1670 Anniversary Inks - Stormy Grey
and Rouge Hematite
J. Herbin has some very nice inks in general -- and these two colors are ones that look quite intriguing!
Pigments Pearl Ex Color Pigments
This can be either mixed in with existing paint, or a binder such as gum arabic can be used to create new paints for yourself. I've used this in both ways before, and it works pretty nicely overall. Sennelier Dry Iridescent Pigment
Out of all their dry pigments, I really could only find one which was iridescent. Sennelier is, in general, a very expensive paint brand, but a little bit does go a long way...
Papers Glitter Pastel Paper Stack Glitter Jewel Paper Stack
This brand is not good for drawing on, but I've used it as a backing for some notecards and such. It's solid and steady, and cuts well. You can layer on top of it nicely, too.
It's a good accent!
If you have any suggestions or recommendations, I'd be more than happy to see what you all suggest!