Flat (hiragata) kyusu with handles (non-hohin/shiboridashi). Love 'em or hate 'em? I have tried three, settled on one as my main for sencha, and plan on getting more at some point. I find they sometimes require slightly higher temps, as they cool much faster. Preheating also helps. I think I prefer not only the looks but also the taste resulting from their steeper "temperature gradient", but haven't blind-compared in a pure shape-vs-shape taste test with glazed teaware (yet).
Anyway, if you're looking for/at flat kyusu, there are many makers. Some do them a lot or even specialize in them (like Jinshu). Maybe this list will be helpful for getting an overview of what's available, but I'm also sure I'm missing a lot of good stuff because I don't read Japanese (further suggestions welcome). Also, many of the makers are available at more than one western-oriented shop, and buying via proxy service from a Japanese shop is possible and easy enough as well. Some are hard to find / out of stock but included here because I found them impressing.
Flat kyusu with inner glaze is another topic. Sazen sells a cheap yet good Hasami-yaki but it's been out of stock for a while. Ippodo sells something similar, but the price is maybe a bit too high for what it is. See also FUJITA Tokuta below.
FUJITA Tokuta tokoname, ball
mogake back-handle flat, also available with inner glazing
Gafu (ITO Gafu) tokoname, ball
black, wide bottom
black in cool shape
with sheen
ISOBE Teruyuki tokoname, sesame (signature stamp patterns, pastel colors)
colorful stamp pattern
colorful radial pattern
mogake & stamp
yohen & stamp
Jinshu (ITO Seiji) tokoname, sesame (makes a lot of flat kyusu, has a signature filter; various shapes and looks: cylindrical/more rounded, carved, mogake, plain, yohen, some dobin)
yohen
plain shudei
without the special filter
carved botanics
carved maple
mogake
mogake dobin
Junzo (MAEKAWA Junzo) tokoname, sesame (many different styles, some with a filter similar to Jinshu's)
antique/rustic
hon-shudei
"zero saturation"
white porcelain with outer glazing
KONISHI Yohei tokoname, holes directly on wall (very famous potter, son of Yusen I below, Yusen II is his brother)
anagama-fired pot with smaller lid opening
another one
tiny 70ml
Koshin (KATO Tadaomi) tokoname, sesame (signature brown marble mogake)
brown mogake, pine bark texture
same but with persimmon lid
MIZUNO Hiroshi tokoname, ball (apprenticed with Yamada Jozan III)
rounded
zogan
MIZUNO Yokei tokoname, sesame
spectacularly angular yohen
rounded yohen
MURATA Yoshiki tokoname, ball or holes directly on wall (known for his hammered pots)
super-tiny (50ml!) hammered surface pot (page removed)
large yohen / hammered surface
two surfaces, hammered and cut
another one
OGAWA Jinpachi holes directly on (pinched) wall (no serial production, only one-offs; works in Kasama, but doesn't call his stuff Kasama-yaki)
rounded flat with conical (comical?) lid
"chestnut skin"
Sekiryu / Sekiryu kiln tokoname, sesame (does a variety of flats, incl. flower carving & mogake)
flower carving
plain black with red line
mogake by TANIKAWA Jin at Sekiryu kiln
mogake by KAMIMURA Hiroyuki at Sekiryu kiln
yohen, uncredited at Sekiryu Kiln
Setsudo (YOSHIKAWA Setsudo) tokoname, ball (polished outer surfaces, sheen, often prominent feet, artistic, well-balanced shapes; famous for the pots created with his older brother, engraver YOSHIKAWA Kodo)
yohen
Shukei (KATO Kazufusa) tokoname, sesame
wide-bottomed flat
UMEHARA potters at Gyokko kiln tokoname, sesame (good value)
Umehara Koushi
U. Koushi flower engraving
Umehara Yukitaka
Umehara Hirotaka
yohen biri, uncredited Gyokko kiln
U. Hirotaka yohen at a very good price, if you're in the US
YAMADA Yutaro tokoname, ball, mogake or plain
black mogake
hon-shudei
mogake
YAMAMOTO Hiromi banko, ball
tiny kyusu with very fine filter
Yusen I & II (KONISHI Yusen) tokoname, holes directly on wall for flat kyusus (known for nerikomi and green mogake pots)
Yusen I nerikomi
Yusen II nerikomi
edits: removed reference to Isobe Ceramics as it doesn't seem to be connected
Flat kyusu makers
TAD inducing looking at all your links. The hiragata kyusu with large sasame filters are especially appealing with slow pouring long fine needle gyokuro.
I think that's the best use for the large ones covering a good part of bottom. They also pour exceptionally well with fukamushi, without the slightest hint of choking, but are more effort to clean afterwards. I think it's not just the larger number of holes, but the fact that it's on the bottom and gets dry particles on top when you put in the tea, which then expand.