Well here are some more ideas, but i'm gonna keep them all in one thread because it wont be as spammy:
Stunt Time
in thise gametype, you have to get as high a stunt score as possible, and unique stunts give you points instead of cash. person with the most points or first to reach the score limit wins!
SPANK Hoard
the aim of this team game is to have as many SPANK packages in your base marker at the end of the time limit. SPANK packages are spread out across Liberty City, and driving through one will pick it up. You can only carry 5 packages at a time, and you must get them back to your base which is a giant mission marker where they will be dropped in the marker randomly. enemies can pick up packages from your base to take it back to theirs, so its both a game of searching, offense, AND defence all in one. you could also set it as an option to win if one team has every package in the level
Cops & Robbers
this game has 1 randomly selected person as the bad guy, and everyone else are cops. The cops try to kill the robber, and when the robber is killed, the person who killed him becomes the robber. you need to stay alive the longest time as the rober to win
Full Wing Dodo Disaster
There are tons of Full Wing Dodo's flying about. When one is destroyed, it drops a package that you mush collect. The person with the most packages wins.
Tank Battle
Each player starts in a tank in a random part of the city. The tanks are modified to have the explosions be like petrol bomb explosions (which enough of can destroy tanks). Simply kill as many other tanks as possible (you cant get out of your tank)
RC Bandit Deathmatch
Everyone is controlling RC Cars and are trying to destroy other player RC Cars with a flamethrower attached to the front of he car (getting hit by flame instantly kills them)
Tanks & Whoopies
same as the cops & robbers, but cops are replaced by tanks, robbers replaced by whoopies