on the acoustic - DiAddario Acoustic lights, 10 gauge
on the Strat - Fender electric lights, 9 gauge
on the Taylor T5 - Elixir electric extra lights, 8 gauge
usually I use DiAddario Electric light 9 gauge on the Strat. So does Carlos
The other guitar player uses mediums, 11 gauge and keeps getting lights for some reason and gives to me. I have some Dean Markley's to try. Never did them before.
For years I used Ernie Ball Super Slinky (9 gauge) on the Strat. Good string. I just want something less "springy" now. Both the Fender and the DiAddario fit that bill.
On the acoustic, I used extra light acoustics up to a couple years ago, 9 gauge. When I finally started playing with other folks and my guitar is a 1981 Ovation, deep bowl, grand auditorium style body, I found that dreadnoughts totally drowned it out. I was told to switch to heavier strings and I went up a notch to acoustic lights 10 gauge, usually DiAddario, but Ernie Ball Earthwood sometimes. The guitar got louder, the tone got fuller and deeper. Harder to finger, but good for strengthening. You get used to it real fast.
The T5 came with the ultra light Elixirs. I did not like the feel of them, too slippery as they are coated strings. Too light also. The strings bent under my fngers at times when playing chords aggressively (not hard). Now after playing them for a while and being too lazy to put new strings on, the coating has pretty much worn off and they are getting dead and I like them a lot better.