The most common Quake-style terminal in Gnome seem to be Guake and Tilda, but they can't split to show several shells in single tab like Yakuake can. Is there any alternative which can do so?
Try Guake with tmux to get the splitting feature.
Alternatively there is a new experimental project called Terra.
For more information check out the WebUpd8 article.
You can write a small script to make any window bring to the front. Though it is not sliding down from top like in quake it serves the purpose. I'm using terminator as my grid terminal since its very powerful.
The script I'm using for this is given below. So first install terminator and wmctrl then put this script where you keep your scripts and add a shortcut key (eg: Ctrl+`) and your done.
Now when you press Ctrl+` terminator comes to the front and press the same once more, it will go to the back of the other windows.