Depens on what game :3
In Yellow , mostly of the time Flareon or Jolteon , since I always choose Squirtle as my starter...
In Gold I 'cloned' my Eevee , and let the 'orginal' pokemon be an Espeon , the clone an Umbreon
In Fire Red it's the same story as in Yellow...
And in Emerald , I didn't let it evolve..because I like the animation too much xD
I'm going to breed it , though