Full-screen apps? No problem! Press the home button, then use the sticky notification. "Kill This" will kill the most recent foreground app for you, even if you're on your Home already.

What could be easiest than this?

No rooting, just pure stock joy!

After downloading the application, just start it once and it'll install the sticky notification for you. (it also installs the notification automatically after reboot)
The notification is a nice little notification with stock looks. No vivid colors, just a handy little (x) icon.

Tested on Nexus One 2.3.3, G1 Cyanogen 6 and various emulators.

Please give me a good rating and send any bug reports / ideas / questions to adroid@ymail.com .