Rammus is the only supporter with which i deal more than 1.5 times as much damage as the adc in average, so he is pretty strong, also he can take much more damage in the same time. He also is capable to win a 1 v 1 vs the juggernauts. Even as a support.

Roll in an unwarded bush until you reach a high speed, aim for the adc, let him attack, push w, he will stop attack, taunt, he must attack, if your adc isn't sleeping, the opponent adc should be dead now.
In late game when you want to destroy a tower even when the creeps are nowhere near an enemy tower,just go with your adc to any attackable tower, put on your w and attack the tower together and it will fall very quickly. Btw that's sneaky and most opponents will get pissed, what decreases their capacity of correct decisions :P

Try to only execute the big minions to share the gold with your adc, never aim for the small ranged creeps. And don't steal farm.

Why would you do that??? First of, Rammus q and ulti scale with AP, secondly: when you got 300+ armor and an adc attacks you, you almost heal the damage taken by reflecting damage through thornmail and your w. Also when you initiate a teamfight 5 v 5 your ulti heals you almost full every second while the fight is going on

Pros:

-Almost invincible in every kind of fight
-Deals tons of damage to the targeted champion
-AoE Damage with his ulti
-Can push towers without any creeps mid to late game
-You will win most likely
-Can take down a minion wave within seconds if neceserry (when they target you and you activate w)
-Great for ganks
-Beats any AD based champion in a 1 v 1 situation (only exception is Darius with either Lord Dominik's Regards or Mortal Reminder, as he has up to 70% armor penetration by that)


Cons:

-No space for ward item late game
-Can't kill overly ranged mages on his own
-Has no ranged abilities