[sampreader]

SetPlayerRunSpeed(playerid, maxspeed);
SetPlayerStamina(playerid, level); -1 = infinite

Disable car blips on map (already mentioned)

Possibly make all player animations server side (onplayerupdate shows them, but does not display to connected players)
Create better sync for people with 100+ ping

Decrease players ping's

Update player movements more frequently

Identify corrupt packets on query

Prevent player keys

Make all animations the same speed regardless of FPS (swimming shooting running...)