I bought the camera with the 25 1.8. I really like it, however I wish I would have bought the 17 1.8 as I have learned I like that field of view more. It's personal, but I think that you will get a lot of 17, 20 or 25 recommendations
For vacation shots I use Lumix 14-140/f3.5-5.6, and the Olympus 9 mm body cap lens. I usually have the 14-140 mounted, because I can pretty much do any shot with it. In low light I use the Lumix 20mm/f1.7.
I carry around with my on a daily basis. With the Lumix 20 mm/1.7it fits in my briefcase. It is a perfect combination I think.
I use it pretty much exclusively on my Panasonic G5. I do have another camera though with a 35mm equivalent lens. I'm fairly content with just these two focal lengths. I use the 60mm for portraits, flowers, cyclocross races, vacations and general family photos where I am able to get a little distance from the subject.
Oly 12-40, bought used. Awesome lens and very sharp. I carry it on a wrist strap, no hood. I've found the hood doesn't help and the lens has very little flare under any conditions. It also keeps the bulk and fiddly bits to a minimum.
When out 'shooting', I also carry a Samyang 7.5mm f3.5, an Oly 40-150mm f4.0-5.6 R, a spare battery and 26mm of Fotga automatic extension tubes in a ThinkTank Mirrorless Mover 20 bag. I am back to using the 40-150 and extension tubes for closeups of spiders because it also lets me use the popup flash on my E-M10.
When I take just one lens with me it's usually the 17mm/f1.8 or the 60mm macro - depending on my goal. Most of the time I take just both with me, especially now in the fall where I can easily put 2-3 lenses in the pockets of my jacket. I also have the 45 f1.8 & 40-150 and like them, but use them much less.
If I could only have one lens for my E-M10 it would be the 12-40. It spends by far the most time on my camera. I will sometimes leave it at home so that my other lenses get used and aren't resentful towards the 12-40.
I love PL25 & E-M10 combo. Very effective IBIS with this lens in both stills and video. Surprisingly good C-AF in video wide open. The images with this combo require no post-processing at all. Just shoot jpeg and it's perfect.