Putting the Sons of Horus up as one big army to begin with, and if there are no bites it'll likely get chunked up into lots. There's also some old Inquisitor 54mm stuff, a few long OOP 40k and Mordheim models that I never really got around to completing (cough 15-20 years ago cough), and a Tzeentch Renegades warband that's also been in progress for more years than I care to count.
Couple pics of things going up: