Actually, there are a lot of games which no-one even bothered yet to modify and there is a lot potential left in it.
A few known examples:
-Final Fantasy XII (12) - International
-"Ultimate Sony Multi-Loader"
You will find some stuff regarding and surrounding that kind of thing on alucard.cc, formerly known as "PS2ModzParadize", thought.
Btw.: There is a Homebrew-LUA-Player available, right here in this board. Just search for it.
PS2 V7/DMS3 V2 (FW:2.4b7); Seagate Baracuda 200GB
PS2 V7/CC1.0 (FW:34 hacked v2 BM:2.1.6); Maxtor DiamondMAX9 PLUS 160GB
PS2 SCPH-30004R; NoMod+NoLaser
3xSony MC 8MB
MAX/Datel 16MB with Boot-CD
Custom FMCB 1.8b+ Beta-Build, my AIO 0.5, Sony&xRhino-Linux