My girlfriend uses a spreadsheet for her engineering work. She constantly complains about Excel running out of memory and crashing, and her work won't authorize the 64 bit version.

Basically she's importing time series data from sensors around the production plant, and then doing fairly complex engineering calculations. All of the formulas are pretty much textbook or derivation/substitutions thereof (e.g. different units, etc), but it's really crazy seeing them written as single line Excel expressions. She spends hours debugging single expression errors in the formulas written by herself and other engineers.

Since you asked for 2 examples, I used a spreadsheet for hosting cost estimation.