That depends on what I'm doing at the moment, but I like my Pigtronix Echolution. It's a really versatile delay and I have it on all the time, when it's not doing delay I set the delay time short and low in the mix so that it's doing a nice ambient reverb type delay with a slight modulation and tremelo in the mix. It's always on!
Otherwise I like my Tubescreamer, I use it a lot too.
