disposable with a coupler if I need several tips used with the same color; parchment for small amounts (no coupler); featherweight for the icer tip only (size 16 featherweight). 
Darn, the parchment didn't come up.
I don't know why, but I never could use parchment bags. I see that Toba ONLY uses parchment bags so I'll have to try those again; I have a full box.
I had heard that there are some food safety issues with featherweight. . .I like featherweight AND disposable, but if I were to go into business one day I'd probably use only disposable as, according to some research, it saves money.
Nglez09 - What research told you that buying disposable bags saves money? I have never seen this, but I am certainly most curious.
I use all three, depending on what I am piping.
Theresa
I use parchment for everything- I cut the tips off for fine lines and use a coupler maybe twice a year.
I only use a pastry bag for whip cream.
I use a pastry bag for my speed icer tip.
mpc
I read it on the Kopykake site. And it makes sense; you don't pay for a dishwasher, electricity, hot water, etc. Certainly would save a lot of trouble.
http://www.kopykake.com/cd_decorating_bags.html
I use primarily parchment, but when I do many decorations in the same color and same icing, (like maybe a border and writing in the same color, or flowers and another accent in the same color) I use a featherweight and just change out the tips. That worked very well when I did a moncromatic cake!!!
I use all of them but mostly Disposible. Less mess when i'm all done. I Love working with the feather weight bags though. I use parchment for quick jobs and small amount of icing.
I use featherweight and disposables. I don't use the plastic bags because it takes more pressure to squeeze which long term leads to hand injuries. My hands were shot until I switched to Swiss meringue buttercream and threw away the plastic bags. Now I have no pain, it's great!!!
Andrea
I mostly use featherweight because they are easier to handle. If I am using a dark color or small amount I will use parchment. The disposables are okay but require more pressure. I don't worry so much about the cost. I get disposables 100 for $8 and featherweights for a little over a $1 for 12 inch so either way they cost pennies. 
i use all disposable except for my white icing bag. i guess i'm just lazy, but it is much less time consuming in the washing department to use disposable when you have 20 colors. featherweight get greasy, to me, after you wash them a billion times. also, it saves me a little time in the decorating area because you can see right off what the colors are in the bags instead of having to look into the bag.
Is there somewhere I can catch a tutorial on how to fold up the parchment into bags? I've never tried that, and it seems like that would be the way to go on just tiny amounts of colors, etc.
I always use the disposables. 18 inch size for the icing tip, and 14 inch Kee-Seals for the rest. I will, on occasion buy the Wilton disposables, but I've found they're pretty weak and sometimes I have "blowouts" with them. 
Any help on the parchment thing would be great! 
--Knox--
Knoxcop1, here's a "tutorial": http://www.baking911.com/decorating/pb_prchmtcones_pg2.htm. HTH.
I use Kee-Seal 12" disposables for almost everything, and the 18" disposables for the icer tip. I absolutely hate the featherweights, I never felt like they were really clean and they stain with colored icings. I use parchment for most colors and I always cut the triangles in half and make twice as many small bags. This is great when you only need a little of a color for FBCT and such.
Quote by @%username% on %date%
%body%