it all depends on whats your favourite element of the three but i would pick vaporeon.flareon is pretty cool too.oh,iforgot to about umbreon trust me pick umbreon.
Damnit! A shiny eevee! Well, since I like Jolteon I'd say THAT ONE! But if you're not too bothered then I'd say go for the more different shiny colours because Jolteon is only more paler when in shiny form. Probably Espeon or Umbreon?