This is a tough question to answer...Atrovaginata throws very long rhizomes but does not produce many culms along them very quickly; Rubro & Bissetii run like mad and produce tons of culms; my unidentified ground cover Pleioblastus - probably Pygmaeus aff. spreads like mad; but here are 4 other candidates.
I may have to give SY Kimmei the most aggressive award as I mow, rhizome prune, and make many divisions just to keep it in bounds and currently it is a tad out of bounds. Lots of spread and culms but not much size early on 6-7 feet at the tallest, also not as hardy as stated some top kill at +3F and total leaf loss. Here is what I've left after 5 years from 1 small plant, it's pretty much a 5 foot tall ground cover and perfect for a perennial shrub in my climate.
<img src="
http://www.bambooweb.info/images/bamboo/2006kimm2.jpg" alt="SEMIARUNDINARIA yashadake 'Kimmei'">
Another candidate, Hibanobambusa Tranquillans this is the spread from 1 plant 3 years ago, I've made a couple of divisions and pruned a bit to hold it back. A bit shy of 8 feet tall so far, this species seems leaf hardy to about +5F, with damage starting about there. Culm kill at around zero.
<img src="
http://www.bambooweb.info/images/bamboo/2006hbtrans.jpg" alt="HIBANOBAMBUSA tranquillans ">
Semi Okuboi in another planting I've been cutting down and digging up, this one is from 1, 3 year old division that has been mowed to control but more needs to be dug out now (and weeded).
<img src="
http://www.bambooweb.info/images/bamboo/2006okuboi.jpg" alt="SEMIARUNDINARIA okuboi ">
And the very beautiful Sasa Tsuboiana is now getting mowed back. This is from 1 very small 3 year old plant. It's about 4 feet tall and covers more ground than the picture may suggest. The poor little F. Rufa on the right edge is getting very scared....
<img src="
http://www.bambooweb.info/images/bamboo ... boiana.jpg" alt="SASA tsuboiana ">