Tcl is my favorite scripting language for these five reasons:

+ It combines macro ish text substitution with really, really, really good scoping and loop constructs.

+ A built in event handler is awesome.

+ Tk widgets look just fine for the one off GUI that routinizes a single repetitive task.

+ (Surprisingly) I almost never need float math in a script, one of the things it's not good at.

+ Tcl doesn't try to provide what should be done in C anyway (Python, Perl, Ruby I'm looking at you....)