OVAs

>>25679
Black Rock Shooter, Tamayura and Houkago no Pleiades started as OVAs but got anime series continuations. (Watch BRS only if you like CG).

Time of Eve was a series of ONA that was later composed into a movie (watch the movie).

Gundam Unicorn, but I only watched the first episode.

Freedom
Denpa Teki na Kanojo
Cossette no Shouzou
Yokohama Kaidashi Kikou + YKK: Quiet Country Cafe
The Hakkenden

>>25679
Dragon Half
Sweat Punch -Kigeki (Comedy)
Denpa Teki na Kanojo
Kono Danshi, Uchuujin to Tatakaemasu- Its fujo bait but its cute
FLCL
Detroit Metal City
Golden Boy-watch the dub

>>25714
I mentioned in the opening post that I've seen some of those and I've also seen Sweat Punch.

Yokohama Kaidashi Kikou comes to mind.

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>>25679
Try these breh:
Armitage III
Batman: Gotham Knight
Battle Royal High School
Black Magic M-66
Cencoroll
Deimos no Hanayome: Ran no Kumikyoku
Download: Namu Amida Butsu wa Ai no Uta
Genius Party + Genius Party Beyond
Giant Robo The Animation: Chikyuu ga Seishi Suru Hi
Hello Harinezumi: Satsui no Ryoubun
Hinata no Aoshigure
Mad Bull 34
Mobile Suit Gundam 0080: War in the Pocket
Mudazumo Naki Kaikaku: The Legend of Koizumi
Shashinkan
Shin Cutey Honey
Sukeban Deka
Taifuu no Noruda
Teito Monogatari
Tenamonya Voyagers
Tokyo Marble Chocolate
Zetsumetsu Kigu Shoujo: Amazing Twins

My hard drive with all this crap on it that I usually refer to when I want to give recommendations for this kind of thing unfortunately died recently, but off the top of my head (striking any that you already mentioned), I'd suggest:
>Alien 9 (4 OVA)
>Bubblegum Crisis (8 OVA)
>Candy Boy (7 Net)
>Time of Eve (6 Net or one Movie)
>Space Battleship Yamato 2199 (26 OVA, stands alone)
>Macross Zero (5 OVA, can be watched without any other Macross exposure)
>Tenchi Muyo Ryououki (Two [or three] series of 6 OVA)
>Voices of a Distant Star (1 OVA)
>Pale Cocoon (1 OVA)
>R.O.D: Read or Die (3 OVA, stands alone)
>Yokohama Kaidashi Kikou (Two series of 2 OVA)
>Kyou no Go no Ni (4 OVA, 2006 vintage--avoid other incarnations of this franchise)
>Iriya no Sora, UFO no Natsu (6 OVA)
>Video Girl Ai (6 OVA)
>Koko wa Greenwood (6 OVA)
>Yawaraka Sangokushi Tsukisase Ryoufuko-chan (4 OVA)

If you're counting UC Gundam series like 08th MS Team as "not side episodes," then you should also know about:
>Gundam 0083: Stardust Memory (13 OVA)
>Gundam 0080: War in the Pocket (6 OVA)

And some other things that aren't quite OVAs, but that still seem relevant here. These will mostly be series that aired on TV with a running time equivalent to six 22 minute episodes or shorter, which aren't dependent on any other title or series (i.e., they stand alone).
>Battle Programmer Shirase (5 TV)
>Rec (9 TV)
>Hanbun no Tsuki ga Noboru Sora (6 TV)
>Mnemosyne (6 TV)