TotalView [L1 ] is a high-end Unix-oriented debugger that's particularly important to those working on parallelization. Its scripting language, rather remarkably, is Tcl.

What is TotalView? [L2 ]

    TotalView is a sophisticated software debugger product from Rogue Wave Software, Inc.
    ...and before that, TotalView Technologies, LLC (2007-2009)
    ...and before that, Etnus LLC. (1998-2007)
    ...and before that, Dolphin Interconnect Solutions, Inc. (1996-1998)
    ...and before that, BBN Systems and Technologies, a division of BBN Corporation (1993-1996)   

    Used for debugging and analyzing both serial and parallel programs.

    Especially designed for use with complex, multi-process and/or multi-threaded applications.

    Without question, the most popular HPC debugger to date.

I used Totalview while at BBN - best debugger I've used. To bad no Windows version