Pretty minor, but while working on FedFunds/Eurodollar trading software at a big bank, I came in on the weekend and reconfigured my cubicle walls so that the entrance was in the same aisle as my coworkers, rather than being on the opposite side and having to walk all the way around to talk to them.

Normally I believe that sort of thing involved the maintenance staff, etc, at who-knows-what expense.