I have ALWAYS for no apparent reason nicknamed my starter. Without fail.
It was Bernie the Charizard
Snap! the Feraligatr
Gex the Sceptile (anyone else remember the Playstation game?)
Raff the Empoleon
And Slappa the Serperior
Otherwise I wait until my team has all it's EV's done and reaches level 50 before nicknaming it something great. It's kind of like initiation into my team I suppose, they aren't full members until they're fully trained and reach level 50?
So far I've got Chalybeate(latin for steel or something), Interdum(latin for a Chromium alloy), Clupeus(Bronze when referring to large plates such as a shield), Wheatley(Portal 2), Aurum(Latin for Gold), and Stella(from Stellar as in stars and ****).
In order, Aggron, Aggron, Bronzong, Magnezone, Lucario(SHINY) and Starmie.
I dedicate a good chunk of time to find the right name.