I would argue that FL doesn't really have winter - our cool season is days to weeks, as you know. That's not enough time to establish a competing grass w/i my acres of weeds.
We just took a hard freeze, spring will be "interesting".
My top five are:
Clover (multiple varieties)
Fenugreek
Buckwheat (my chickens ate most of the seeds this year)
Sorghum/Sudangrass Hybrid (my chickens ate most of the seeds this year)
and "melons" (Water, Canta, Summer Squash, Zucc...