For each of my project, a cup of beer with my sub-cond after the FAT is a must. It's indicate a mile stone of the project and it also mean a 100% done on the engineering, although it's not the case for most of the projects.
I don't really enjoy drinking beer, a cup is just good enough for me. However, my sub-cond will give me a bottomless, I think I must be torture him too much XD
It's enjoy listen to the music and singing while having a drink. The most enjoyable part is to talk about the stupid company, peoples and laugh at our stupidity.
I'm not sure about others, but working at site is enjoyable. Most of the time, people will forget about control system, therefore most of the time we are suffering from last minute notice and we did lot of stupid thing at site. That why we talk and curse those stupid peoples that make us do stupid thing.
All suffer that we faced will be forgotten when we celebrate the victory, cheer!