Air Overhaul (Drowning is Drowning) by Mark719
This mod makes it so you die when you drown, like you know what actually happens... The first bit of drowing damage you take will kill you instantly.
JurassicFixx's Mobs by JurassicFixx
JurassicFixx's Mobs adds in extinct and extant animals most mods don't include, or don't give a decent model to that players want for their zoos and parks.
Tainted Magic by John Yorke
A thaumcraft addon in which you will use the evil magics such as flux and warp to your advantage...
Mine Little Brony by Teotoo, Others - see MCForum thread.
Adds more pony to Minecraft! Lots of art by other people, lots of ideas by other people too. See the MinecraftForums for the full credits list.