I like all those mentioned above and I would add microsword, which ever variety you can find, once you get it established it forms a nice lawn.
I wasn't sure which plant would do the best in my new 24 inch deep tank so I put a little of all those mentioned above in the tank. The microsword spread the fastest, the glosso is try to catch up, and the hairgrasses are thickening up before spreading out. The E. parvulus looks like it spreads faster than the E. acicularis. The sag hasn't quite settled in yet.
Ranalisma rostrata can form a nice lawn too, but it is a little fussy about having a good supply of nutrients available, especially PO4.