I'm excited for espurr, joltik, dunsparce and chikorita! Also hopefully we'll be able to get zygarde core form too because I love that squish. Most excited about Chikorita at the moment though because that's sooner!
If you mean on LV... I give you one guess on which one I'm waiting to catch. Although I will probably be waiting a while...
There are so many! I'm excited for Hoenn region mons the most though because a lot of my favorites are from the region. Some I can think of on the top of my head are Roselia, Gardevoir, Flygon, Milotic, Metagross, the Regis, Lati Twins, and Jirachi.
Totodile, Skamory and Raikou are some of the mons I'm waiting for, guess is good all these a gen 2, I have many more but these are just the wants I'm having the hardest time to wait for right now. XD
Kingdra, I suppose? I don't know what's coming next, but of the things I was told about, that one appeals the most to me. The rest I'll just play it by ear as I go along, I believe. I'm rather ordinary, I know.
I'm waiting on my favorite starter Treecko! Also, in close second, Cyndaquil! Apart from those, I'm excited to be able to (eventually, hopefully) catch Tyranitar and Sableye.
I right now want to catch an eevee 'cause I want Flareon or Espeon. Each time eevee appears, I throw a great ball but still it escapes!