I started the first ep of 0080 since David Hayter voiced one of the characters but I didn't really care for it. But I have heard nothing but great things about it; I should probably give it another shot.
I would suggest 0083 first. It's shorter, so you can sorta get it out of the way. It also does a great job of bridging the gap between 0079 and Zeta. It's a wonderful example of high quality hand-drawn art and animation. And I mean that sincerely, not like Doan's Island QUALITY.
My personal favorite is 08th MS Team, but it's a tad long compared to the other OVAs.
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