[Pete Bony]

Here's a question that could easily get a thousand different answers but hopefully an education for all of us.
What's your favourite fly and just as importantly why? (Maybe you could also say if it is for small/large  still waters , rivers or whatever and how you fish it)
Mine is a Pheasant Tail  - Both weighted and fished on an intermediate line and unweighted fished on a floating line with a slow(ish) figure of eight retrieve. I fish smaller still waters and found that most variations of pheasant tail would often bail me out from having  a dry net when the trout were being a bit "finicky".  Next to that would have to be (Definitely not for the purists) an egg fly - The egg fly (Fished under a sight indicator) will normally catch at any a trout or three for you at just about any still water fishery.

[Derek Roxborough]

any of the Invictas, easgach 1

[James Craig]

The Deer Hair Sedge - I've found this to be the only reliable surface fly in my very short fly fishing career to date. I've found it easy to tie and I can churn out a batch of varying sizes in an evening. I think a large part of this fly being productive for me is that I am able to fish it confidently - having first read a bit about the Bob Wyatt ethos, then caught some fish, used the fly some more, persevered when the going was tough, caught some more fish, and so it goes on!

If I'm allowed a favourite wet fly too, that would be the Black Pennell. Not very exotic, but the first fly that I tied on my vice and has proved very tempting to river Brownies in smaller sizes. I have fished this singly on long leaders to good success, throwing it across stream and down which I think makes it work in spidery fashion. I've found any type of nymph a bit hit or miss so far and I've no doubt that that is down to presentation. 

[Dave Medlyn]

Without any doubt, the Bibio. Tied on any size from 16 through to 2 (spey style). Small brown trout and even salmon are unable to resist the power of the dark ( with a blob of red) side.