Essential Doujinshi

Essential for what? Ones that people should have read?

Short list:
domin8me
Life is peachy
Hardcocked
Anipyu
Ovulation Exhibition
Boys Empire
Power play
Momoiro Geshuku Utopian
or Cohabitation Alliance.Also https://www.fakku.net/viewtopic.php?t=97673

Witchraft
Power Play
Strange kind of woman

Guys and girls... don't confuse doujinshi with H-manga... it might not be obvious to n00bs (like this forum's owner), but they are very different beasts ;)

Doujinshi... everything from NiseMIDIdoronokai（偽ＭＩＤＩ泥の会） and Udon-ya（うどんや）

H-manga-artists... Ishikei（石恵） and Kizuki Aruchu（鬼月あるちゅ） (from the circles above), as well as Naruco Haneharu（鳴子ハナハル）

These are essential, personally I have a more varying taste, that is not limited to the three best-selling artists in Japan :p

We don't, but as you said, the OP does, so we're just... humouring him, you can say.

There are some "shining" exceptions that don't... indeed ;)

Doujinshi can be the generic blanket term for any drawn or cg pron. Hentai also covers real porn also since hentai just means perverse. Since we can't. just name a single anime doujinshi that would be essential you have to go ero mango route just to cover a proper list of your not cool unless you read these. Doujinshi =\= fan made but doujin/0\ anime series in theory.

Well, dictionary time ;)

doujin（同人） = literary group, clique, fraternity; as in doujinCG, doujinMusic, doujinSoft(ware), and...

doujinshi（同人誌） = fanzine, magazine published by fans

hentai（変態） = perversion, abnormality

ecchi (Ｈ、エッチ) = to have sex (with する), indecent, lewd

anime（アニメ） = animate cartoon

komikku/manga（コミック／漫画） = comic, cartoon

tankoubon（単行本） = collected volume (collected, as in collected stories from a magazine)