My godson was visiting yesterday and gave me a new acoustic guitar plectrum to try which has quite radically altered my view on picks in general. I'm a perennially old school kind of player and generally use a Fender medium for just about everything.

No more.

The acoustic pick he gave me was a large triangle Dunlop 1.5 Primetone. It was amazing. The difference in tone on my Taylor's and Whecters was astounding.

I've now got some 1.0 Primetones to try with my electrics.

I'll keep ya posted but as per usual in my dotage I'm pretty sure I'm about to learn a new and valuable lesson in spite of myself and my Luddite ways.

I have used Dunlop .60 mm for decades. I like a little flexibility in my pick.
Anything thicker I feel like I'm going to break something.

For decades I used these:
 

 
Now I use these:
 

I used to use Dunlop Tortex for years, but recently switched to Dava Grip Tip Gels for both electric and acoustic.
Noticeably less resistant on the strings and less clicky pick noise on the acoustics.
 

That's two votes for Dava. 
 
Here's a neat group picture from Dava that includes both of the picks mentioned.  I've never tried the Grip Tip Gel's yet...  Guess I'll have to now!
 

Much depends on attack choice, but after pleking my main I have been using the pick it came home with which is very light and pointed. The point has been more useful than expected and I had it pleked with 10s, so very little force is required to play it.

Flip side is hard/bright attack on heavy strings. I have gone all the way to using Thai 1 baht coins (same reason as Brian May for the serrated edges). Not used often anymore as they are too bright on my pups.

It really comes down to choice. I have taken a shine to thumbpicks recently and been looking into these more. I want to try out the Fred Kelly Slick Picks but not ordered any yet (elderly.com does custum orders which is nice for odd quantities). The ones I have hurt for prolonged use, so need some real ones.

I was skeptical when reviews said the poly gels slide over the strings like glass, but I took a chance, particularly since they're not cheap as far as picks go.
I was won over in about 2 minutes.
 
I trim away a bit of the rubber part to expose more of the gel part.
Oh, and they're not very pink - see through pinkish is more like it.
 

Depends on the style of music I'm playing.
 
Most of the time, .88mm tortex. Work well for most of the hard rock, metal stuff I play. I also love them for bass.

 
If I'm trying to do sweep picking and such, the thicker the merrier. Usually, 2mm works fine.
 
For things that swing and groove, yellow, .73 mm.
 
For SRV-type of thing, I'd use those yellow ones but play with the large end, holding the narrower side. It just sounds more SRV-ish that way to me.
 
These (used in the same fashion) used to be my weapon of choice for that.
 

I've always been too lazy to use a pick, preferring fingerstyle for everything (even lead - I use my thumb and 2nd finger for single note runs), but on the occasions when I really want that pick sound, nothing beats Jim Dunlop Big Stubby (the grey nylon ones, not the blue transparent ones). I use the 2.0mm. They just have a very solid, consistent sound, glide over the strings wonderfully and last ages. 
 

Rain
 
 

I use the .73 version of the Jim Dunlop above... I sweat a lot so I like the grippy nature of the JD nylon pics...