We all have our favorites and what one cheat would you not be able to live without (you don't have to necessarily use it all the time) and just love more than the others? I'll try to list the most popular.
What Cheat Do You Love Most? 98 votes
MoveObjects because I can make all sorts of things and my favorite- I can pick up my stuck Sim if I need to do that.
Motherlode and Kaching! I don't have time to work for all that money!
FamilyFunds since it makes it so easy for me to move a bin family into any lot!
45DegreeAngleofRotation, because I love decorating a room in reality with seating etc. at an angle like real life.
CEF because I love to build split levels, homes inside a mountain etc., any terrain tool cheat is worth it's weight in gold!
CAS cheat, I love putting my Sims in hidden outfits!
SnapObjectsToGrid, because Maxis never lined up the grid for coffee tables, paintings etc.
All of the above, I use them often.
"Games Are Not The Place To Tell Stories, Games Are Meant To Let People Tell Their Own Stories"...Will Wright.
TS4 without Terrian Tools is like Windows 8 or 10 without the Start Menu.