Love Aranea... I think I even used them in an old-school D&D campaign... I know I used 'em in the Isle of Dread. I really want to run that recent Dungeon adventure that features them, too - Aranea are a lot of fun.
I ran a stone Animated Object in a fight in the "Ghoul City" the PCs were investigating. Strangely enough, that encounter wound up being tougher than most of the ghoul packs the group had been fighting, but I think this was due to the fact that they were prepared for ghouls... they weren't prepared for a construct with damage reduction. It was really good, because the group *still* thinks they had come up against a gargoyle....
Allips are a fun undead to use, but like a few others, I get rid of their permanent energy drain and just make it temporary (upping it by a die code in the process) and drop their CR to compensate. I prefer shadows, though...
Finally, Unicorns are a fantasy staple. I tend to bring them out when the group has at least one female in it, because women seem to respond well to Unicorns. Fiendish unicorns are great, but they're even better as a plot hook (you'd be surprised at how readily most of my female Players jump at the opportunity to save a unicorn from a demon of some sort).