The monsters I consider useless and/ or ridiculious are: MMI: Achaierai, Beholder, Cloaker, Digester, Displacer Beast (I use em... but their stupid looking and a dumb concept), Etheral Filcher, Ethereal Marauder ( I think I saw these in Tremors 2), Gibbering Mouther, Phantom Fungus, Rast, Ravid, Tojanida, Xorn, MMII: Ash Rat, Avolakia, Bladeling, Boggle, Bogun, Bone Ooze, Braxat, Cloaked Ape, Cloud Ray, Corollox, The Abyssal Demons, Desmodu, Ethre Scarab, Ethereal Slayer, Fiendwurm, Fihyr, Flesh Jelly, Galeb Duhr, Glimmerskin, Grell, Leechwalker, Linnorm, Loxo, Moonbeast, Mooncalf, Morkoth, Needlefolk, Nimblewright, Psurlon, Ragewind, Raggamoffyn, Rampager, Red Sundew, Rukarazyll, Stone Spike, Teratomorph, Windghost, and Wyste
I could go on, I have more monster books but after MMII this has become quite tiring

. It's almost disappointing to think I have to pay for some of these wastes of pages. I'm not a big fan of the "what if we crossed an ape, octupus, and fly together" type of monsters, they're not original and have ridiculious concepts. If I can't resonably describe the monster and have to resort to showing a picture, I don't like it. A perfect example would be the Fihyr or Grell.
Another big point is they're quite a few good monsters out there, that are completely ruined by dumb or effortless artwork. You try to use them then the players ask to see a picture and the creature's ruined.
Obviously I'm picky, but these books aren't cheap. I want my money's worth when I buy something, and I don't want something that's tossed together with no thought or effort. Many of these stupid monsters wouldn't even get a second thought if made by non-WotC companies. That's why I like the Creature Collections
