So far for roundwounds I use EB medium slinky's and DR Nickel Low Riders. I am goin to try flatwounds on my Peavey bass soon though as I ordered a set of light D'addario Chromes.

I use flats pretty much exclusively, except for a few basses that have rounds, though I usually change what strings those basses have.

I use:
LaBella Tapewound flats
LaBella Jamerson Signature Flats
LaBella Deep Talking Flats (Heavy Gauge)
GHS Precision Flats
Pyramid Gold Flatwounds
Rotosound Jazz Flats LE
Rotosound Trubass

Rounds I use include
Rotosound Swing Bass 66
Pyramid Gold Rounds
Optima Gold Rounds

EB Reg Slinky. 4 and 5 string sets hopping to be able to use 6 string sets soon.

i use slinky