I keep both condoms and KY gel in my plumbing kit. I get some strange looks when people see them and jump to conclusions.

I use the condoms to plug drain and vent lines. They can be inflated to block water or air flow so pipe can be added with less trouble, stink or mess. Once the assembly is complete I thread a plumber's snake down the line with the tip configured as a sharp barb. This slips past the inflated condom, and when drawn back, both punctures it and catches it so it can be removed.

KY is a very good lubricant and good for lubricating O-rings, seals and slip fittings no matter what rubber or plastic compound they are made of. That and it washes away cleanly. Other lubricants can damage incompatible materials, are less slippery, don't wash off when you want them to, and are more expensive.

That, and you never know when your going to run across a lonely lady with a 'repairman fantasy'. It hasn't happened yet but if it does I'm covered.