Sonic Adventure Hacks & Mods
Sonic Adventure DX: Fixed Edition
Sonic Adventure DX: Fixed Edition is a mod for Sonic Adventure DX PC 2004--with partial support for Steam/Dreamcast Collection and others (GameCube & Dreamcast)--which contains various fixes in relation to item layouts, textures, models, sounds, and more.
Download: Sonic Retro thread.
Input Mod
Fixes camera issues with XInput controllers, enables rumble, fixes triggers, etc. Doesn't yet have configurable controls.
Download: All Releases (GitHub)
Instructions & Info: Sonic Retro thread
Idle Chatter
Press the Z button to hear what your character has to say.
Download: All Releases (GitHub)
Pause Hide
Press X+Y to hide the pause menu like the Dreamcast version. Great for screenshots.
Download: All Releases (GitHub)
Smooth Cam
Makes first person camera full range and variable speed instead of 8-directional fixed speed. Video below.
Download: All Releases (GitHub)
Chao Spin Swap
Swaps X and B buttons in the Chao Garden. X to spindash, B to grab your Chao.
Download: All Releases (GitHub)