These wouldn't have to be official modes, server scripts would be fine.
1. Juggernaut
There's one randomly picked player (The 'juggernaut') who has a lot more health then usual, and is alone on their team. The other team has normal health, and has to take down the juggernaut player before the juggernaut takes the intel.
-This mode could also be reversed, instead the juggernaut would defend his/her intel from the other team.
2. Build and Defend
At first the teams have a certain area that must stay within, which is the area where they have to build their base in a limited amount of time before the game starts. Then the game proceeds as a normal CTF game.