As a heads up, there is also Yakuake, but it bites bigger than roadkill on a summer day. It's buggy as all crap, don't know what's up with that. It has no tray icon, and the way to exit is pull up a regular terminal and type "killall yakuake". Why I mention it, I have no clue, other than it seems to take a slight bit less screen real estate (but can't be rolled up either). There also is no option to make it transparent, one only has the default KDE terminal themes to choose from, as it's based on Konsole (but even Konsole in KDE3 had that option). Also, I can't figure for the life of me what the teeny buttons are at the lower right of it, except for one of them; they appear to do not much, with the exception of making you *think* you've exited and quit Yakuake when you haven't. Click that thing, then try to bring up Yakuake again. It's still there, and will trigger a Yakuake Notification that says nothing. Figures. KDE's good for that these days in general:
(Yes, I know the size of both Guake and Yakuake can be edited; that's not the point. They take up the screen real estate by default, and that's pretty huge for both of them. I like the size, I just don't like that it's "always on top" with it, with no other option to get rid of it other than to hit F12 or some other key of your choosing, which minimizes it to the tray. Maybe I don't want to minimize to the tray? Why not just roll it up to get it out of the way for that three or so seconds you need it out of the way?)