Here are a few I've used in the past or recently discovered:
Echo("\c1grey \c2red \c3silver \c4blue \c5purple"); - Echos colored text in the console window (\c1 - \c5).
Tree(); - Opens up a tree view of all groups, sets and objects associated with the server and / or client.
Trace(%bool); - Shows a hierarchical view of all functions that are running (a %bool value of 1 enables it and 0 disables it)
BackTrace(); - Echos the order of functions associated with the backtrace (when executed in the console, it just echos ConsoleEntry::eval);
Error(%str); - Echos red text in the console window along with a backtrace of the error.
Warn(%str); - Echos grey text in the console window.
Metrics("fps"); or Metrics(fps); - Shows your client's current framerate (metrics(); disables it, but returns a warning).
mFloor(%float); - Returns the floating point value rounded to the preceding whole number.
mCeil(%float); - Returns the floating point value rounded to the subsequent whole number.
mFloatLength(%float,%numDec); - Returns the floating point value rounded to the nearest value relative to the number of decimal places you specify (for instance, mFloatLength(0.45,1); will return 0.5, and mFloatLength(0.45,0); will return 0).
%Obj.Save(%filePath); - Saves a datablock with all related fields to the file path and format you specify.
%Obj.Dump(); - Echos all member fields, tagged / dynamic fields and methods associated with the object in the console window.