This is NOT the april fools joke about the They Hunger mod on the DS, this is real and in development
Eric Hobbs and I have been working on porting Half-Life to the DSi by using a modified version of Eric's CQuake engine, which itself is a modified version of the Quake engine. It runs so far, but drops to 1FPS in areas with lots of visible textures. Main changes to the CQuake engine is upping the vertex limit to 2048 instead of 1024.
A release can be expected soon, but not right now

Just to give you something to look at, here are some of the config files:
valve.rc:
// load the last saved configuration
exec config.cfg
// run a user script file if present
exec autoexec.cfg
//
// stuff command line statements
//
stuffcmds
// startup stuff
alias +buttonuse "impulse 31"
alias -buttonuse "impulse 32"
alias +duck "impulse 89"
alias -duck "impulse 89"
alias bobstyle1 "cl_bobcycle 0.6; cl_bobup 0.5; cl_bob 0.02"
alias bobstyle2 "cl_bobcycle 0.7; cl_bobup 0.0; cl_bob 0.015"
scr_conspeed 900
// handedness
// left
//exec lefthanded.cfg
// right
exec righthanded.cfg
// open menu
togglemenu
lefthanded.cfg
bind "DSSELECT" "+usebutton"
bind "DSSTART" "togglemenu"
bind "DSUP" "+jump"
bind "DSDOWN" "+duck"
bind "DSLEFT" "+left"
bind "DSRIGHT" "+right"
bind "DSB" "+back"
bind "DSA" "+moveright"
bind "DSL" "+jump"
bind "DSR" "+attack"
bind "DSX" "+forward"
bind "DSY" "+moveleft"
bind "DSTAP" ""
righthanded.cfg
bind "DSSELECT" "+usebutton"
bind "DSSTART" "togglemenu"
bind "DSUP" "+forward"
bind "DSDOWN" "+back"
bind "DSLEFT" "+moveleft"
bind "DSRIGHT" "+moveright"
bind "DSB" "+duck"
bind "DSA" "+right"
bind "DSR" "+jump"
bind "DSL" "+attack"
bind "DSX" "+jump"
bind "DSY" "+left"
bind "DSTAP" ""
credit also goes to the Half-Life dingux and Half-Life PSP teams for the original half-life quake ports.
-TZK