Achaierai - No, but I'd like to
Allip - Yes, and I will use it again (controlled by mindbending clerics)
Animated objects - Hell yes. So many possibilities, though they can quickly grow stale
Aranea - Yes, in CotSQ. They need some forethought, but are usefull nonstandart shapechanger.
Athach - Used them. Nice hulking brute that is relatively high powered and has some minor funky abilities
Delver - Great "plot monster". I look forward to using one
Destrachan - Not yet, but plan to use them a lot whenever possible. Mount, watchdog and artillery in one.
Devourer - No. I don't realy care for this one
Giant Squid - I don't think I've yet used, but, it's a giant squid. Why shouldn't one want to use a giant squid (from hell!)
Girallon - Another "not yet but I'm waiting for the chance"
Gorgon - See Girallon
Nightshade (any) - See Girallon
Phasm - No, and I don't see myself using it at all. So it's a doppelganger in every way, just squishy?
Rast - See Girallon
Tarrasque - Haven't used it and would only use it as plot device
Thoqqua - I'm not sure if I've used one jet. If I haven't it's defenitely in the "Girallon team"
Tojanida - Just to weird not to use, but I haven't jet
Unicorn - Still waiting for a chance to use one as plot device
Will o'wisp - No, and I don't care for it
Yrthak - After the third look or so I decided I realy like this think, so I'll put it into the "Girallon team"