The latest addition to my own fly fishing, and fly tying in particular, are wiggle tails. Wiggle tails are totally awesome, and work really well on all sorts of streamer - big and small. A black Wooly Bugger with a wiggle tail is an unbelieveable slice of life in the water, still or running.
And on the big ones the action is unbelieveable, as you can see in this video. Some people find that the addition of these tails border on "lure fishing", and especially if you also add a rattle, which also introduces soud into the whole "trigger system". I like fishing both rattles and wiggle tails, and sometimes they really are fantastic at triggering lazy pike to a take.
On tube flies it's relatively easy to tie a few rigs, where you can attach and detach the tails depending on your mood. My friend, Daniel, has made a video about his rig here. The smart thing about this rig is that it creates a double loop, which secures the tail a little better.
They do fall off once in a while (rarely) and especially smaller pike can really play havoc with these tails, but generally they are quite durable (which is good, because they're expensive).
Smaller flies also benefit from wiggle tails - a Wooly Bugger looks abosutely killing with a small, black wiggle tail, and on my first test with these, I did exceptionally well in "my" little trout lake (the pic is an older one :-). I also have a couple of saltwater flies with wiggle tails that I look forward to testing.
Have a great holiday!