[Morgawr]

I use something like this on Linux, it's called tilda (there are also various similar implementations). It's both awesome and a curse to me. I have it bound to alt+kp_enter and I always keep an irssi/irc session running on it. Every time I need to chat with my friends on our IRC channels I just hit alt+kp_enter and it opens, it's a curse because now I'm always chatting and doing other things while I work, which detracts a lot from my productivity.

Still, really awesome! Nice to be able to share something like this with our windows friends.

[Tiksi]

I've been using guake which has the same functionality as Tilda but a few extra features (hot-key for tabs) that I can't live without.

[lewaldman]

Same here but binded to F1 and always running it's own tmux session with a root logged terminal, a regular one aaaannnddd a Cmus openend! :P

Nice one about the IRC... will put it on the tmux fourth tab! :D