I don't agree with special attacks being uncommon, however.
That may be just me. I've only be hitting mono-Normal teams lately for some reason. Still, I can never find an opportunity to set up Light Screen. Jolteon would much rather deal some damage.
Special attacks aren't uncommon, it's just that there is a relatively small amount of threatening special attackers : Deoxys (that one's more of a mixed attacker), Reshiram, Kyurem-B, Porygon-Z... what else? Jolteon can deal with all of these on his own, besides Deoxys, but that thing's broken anyway.
Bottom line, I don't think Light Screen is very good on Jolteon.
Honestly, Deoxys should be banned. It's pretty much a requirement to have one on your team right now, and nearly every single match I've had got me to lead with Deoxys, Psycho Boost, OHKO the opposing Pokemon, and sometimes even OHKO the switch-in with Superpower.
But since it's still allowed, what's the best item for it? Life Orb is standard, but Focus Sash can be good if the opponent predicts the Deoxys lead, leads with their Scarfer, and attempts to OHKO you, only to be OHKO'd back (or 2HKO's and finished off by ESpeed). I'm sticking with Life Orb for the moment though, since I've never actually encountered anybody who even attempted to deal with Deoxys.
Cinccino is a beast. Just wanted to point that out. It's just like Ambipom, but with more powerful movesin general. less Attack is noting when you have 125 BP STAB.
Also, it can hold its own much better against Groudon :
252+ Atk Choice Band Cinccino Rock Blast (5 hits) vs. 252 HP / 0 Def Groudon: 280-330 (69.3 - 81.6%) --
guaranteed 2HKO after Leftovers recovery
252+ Atk Choice Band Cinccino Rock Blast (5 hits) vs. 252 HP / 252+ Def Groudon: 210-250 (51.9 - 61.8%) --
approx. 99.6% chance to 2HKO after Leftovers recovery
252+ Atk Choice Band Technician Ambipom Double Hit (2 hits) vs. 252 HP / 252+ Def Groudon: 134-158 (33.1 - 39.1%) --
approx. 4.2% chance to 3HKO after Leftovers recovery
252+ Atk Choice Band Technician Ambipom Double Hit (2 hits) vs. 252 HP / 0 Def Groudon: 176-210 (43.5 - 51.9%) --
guaranteed 3HKO after Leftovers recovery
Edit : People, please stop using Scizor and Aegislash. Not only is it stupid, it also catches me so off-guard that it causes me to nearly lose every time.
Edit 2: Okay, I see why I'm facing standard OU teams. Everybody's points dissapeared. On the bright side, I'm now on the top of the ladder! Hooray!