I have these files:
I want to rename each file so that it will not contain the first 5 characters of the filename. I can write a script that can to the trick using a for loop and inside do a cut on each file name and then a rename.
My question is if you know a tool that can to such things like this and more complicated... For example take the first 5 characters, skip 2, take next 10, and for each file replace "_" with a " ". I can write a script for this too, but if it's already out there I don't want to reinvent the wheel...
Thank you.

Well...how about sed (stream editor) or awk (which is said to be more like a language than just a 'tool')?

EDIT: it's said (among other things) that Unix's philosophy is to do complicated tasks with simple tools rather than do simple tasks with complicated tools; thus using more than one small program, with piping for example, is more recommended than trying to find a huge program that is both heavy and big in size. Why? Since having small tools that, when combined, can do virtually anything you like, is more sensible than having some big tools that can only do certain tasks. Some day you'll invent a task that there is no tool for, and that day you can recombine your small tools to do the job.

So, instead of trying to find a single app you could ask yourself what the job actually is, if it's cut into pieces? Taking filenames from a list that is inside a file - that's reading the file and chopping the information in pieces. Ok. Then take each line and chop it into pieces, separated by certain marks. Ok. Then take only the relevant information. Ok. Then transform some letters to some other letters. Ok. Then put this all into a variable, for example, and do a rename. Ok. To me it sounds like every task can be done with the tools around; having a script around is not a bad thing, but if you like, you can probably do this using just the command line (I'd rather pick up the script).

I know what you're talking about, but when I meant 'tool' I meant something with a GUI, not a command line. I used Windows XP and Fedora Core (3,4,5,6) for years and now I definetely switched to linux and I miss some applications I used in Windows. This is one of them.
I know how to use sed and awk and I know you can do anything with awk, but I need a GUI. And if I won't find it, probably I will write one because I like Java myself... Thank you.

krename may be what you are looking for.
krename

That's what I was talking about... Why waste your time and write scripts when you can use this? Thank you my friend.