Okay, this probably works on all linux boxes, if they're using bash:
You want to repeat a command but you are too lazy to retype it. And it's been a while since you used it, so you don't want to type the arrowkey-up 100 times.
Try this in a shell or terminal window: press CTRL-r, a (reverse-i-search)`': will appear. Now you can type the first letters of the command you used earlier, bash will search prevoius commands and suggest one of them. Type more letters for a better result. Simple, fast and lazy!