Well, in the hacking scene we had lots of people coming and going, but of all of them, I really miss Treecko Lv100 (he's probably at other forums or maybe not, don't know), as he had lots of potential at rom hacking, and is a big loss for PC's hacking section.
Obviously, I'd also like to see Jeremy around here sometime, he's probably one of the guys who made me laugh most, and is a great S.Mod too.
And, I also feel Siggy's absence as well. She probably will come back (as far as I know she did something like that in the past, so I have hopes she may return sometime)