May or may not require an actual debug console in some cases (specifically on the Xbox), but most play on modded systems fine. Feel free to ask more questions, Ive only posted small bits of whats written on the disks. Some I have tested a bit, some I have not.
Arcade
Evil Night / Hell Night Konami M2 - 70$ Disk Only
Consoles
Xbox Debug Kit - 90$ (Note, it is a legit XDK motherboard, placed inside a Halo LE case) - SOLD
PS1 Debug Kit : 95$ (Scratched up, beat up, open/shut a bit iffy, but it works fine. Look at picture, more available)
Xbox
Blink 2 : Early Preview Code - 25$
Speed Kings - Early Code - 25$
WWE WrestleMania 21 - Preview - 20$
Counter Strike - Preview Code with small paper document - 30$
Vexx - For Preview - 40$
Rocket Power Zero Gravity Zone (Unreleased) - 205$ (buy both the PS2 and Xbox version for 395 total)
Phantom Crash - Final / Debug Version - 30$
Crimson Skies & Gun Valkyrie - 50$ for both (Note, I cannot get either of these to work correctly for some reason)
PS2
Sphinx - Review Build (Early) - 30$
Rocket Power Zero Gravity Zone (Unreleased) - 205$ (buy both the PS2 and Xbox version for 405 total)
MLB 2006 Review Disk - 7$ (Prefer to sell with another disk to cut back on shipping)
Indigo Prophecy - External Preview - 60$
24: The Game Pre Tech Check Build - 25$
Amplitude Review Code - 30$
Frequency (Review) (Dumped and Released) - 20$
Mat Hoffman's Pro BMX 2 (For Print) (Alpha Build) (Released I think) - 25$
Prefer Paypal via gift with fee paid, all items shipped using USPS priority mail in a box, usually flat rate regardless. Prices range from 6-14$ shipped-ish, sometimes more.