What should I do with a perfect togepi 15/15/15?

Wait for Generation 4.
Then evolve (TM?), power up Togekiss

You should wait until Togekiss comes out.

Nothing atm. Just evolve and keep him.

I evolved mine. However, I later realized since I already had the Togetic pokedex entry I should have waited till Gen4 because the candy cost to evolve from Togepi to Togetic might drop.

100% Togekiss is projected to be 2719cp at level 30, and 3172cp at level 40. Here's hoping they add some Fairy fast moves by then.

I would transfer it if i were you

OMLET

One of two things I would do:

• if you're interested in legacy movesets and predict that even the crappy ones may have value (think beanie babies) then you could evolve it to a togetic and hope it gets what could eventually become legacy moves for trading purposes, or, probably the more practical use...:
• hold off evolving until gen 4 releases as the candy requirement may drop from 50 -> 25 once togekiss is released, like both zubat and horsea experienced. Unless you're rolling in candy, then option 1 could work?