I want a defense champion because I have friends who like assassins and such, and I want to know what's a good champion for defending your base late-game? I need someone that I can fend off champions while I wait for my teammates to re-spawn, my friends usually play champions that can pick off people and get nice kills, and I just want to be able to make sure I can defend while they do that idiotic stuff :P
Hey man, this is a really open ended question, but here are a few good wave clearers for each lane. Be warned, I am not saying these champs are meta or anything, I am just saying their kits are good for wave clearing.
Top: 
Jungle: 
Mid: 
ADC: 
(Any ADC with a 
)
Support: 
I think waveclear from range is the best way to succeed.
Very late game, if you lose a teamfight and are alone defending against 3+ people, you aren't going to succeed with anyone to be honest. The champions will be far enough in their builds that they'll have no hesitation to dive a turret and try to kill you as soon as you're in range.
So your only hope is to make them dive the turret from outside of range. Meaning you need to waveclear the minions so the minions can't tank the turret until they get to you.
My last game I succeeded as jinx 1v4 at 55 minutes defending the nexus turrets for 25 seconds. I wavecleared with my rockets and forced them to dive me, then secured a double kill and flashed to my fountain. My teammates respawned after they took one turret, we pushed the other way and won.
If you go tanky they'll ignore you and win. If you're damage they'll dive you and win. Your only chance is waveclear in my experience.
I'd say because of her easy clear, heal, and ult the will prevent dying to a tower dive.
Build a little AP, Sunfire, Iceborne - no trouble at all with minion waves. Can't really be dived, either.
Late game Zac is beast at playing defender. Passive + GA makes you very hard to kill, and your abundance of hard cc can destroy a tower dive. I won a game like that once; got a triple kill under tower and forced the other two to run off, and when I pulled myself back together with my passive my team respawned and we pushed mid for the win.
Shen comes to mind. Darius is a toss up. udyr and singed. nasus is kinda a toss up as well.
