A consulting gig. There on behalf of the software vendor as an insurance policy 3 months before go-live.
The entire project was staffed by contractors, with two different consulting organizations "Managing" the project.
I sat on my arse of 3 months (having been sold in at a principle rate even though I was only a senior consultant). Only got asked 4 questions in the whole period. The questions where remedial and answered within seconds.
Spent my whole time day trading, came out £30K up (just before the bubble burst in 1999), got paid over time for the weekends when as they still wanted me there.
Paid for the deposit on my house.