Powerball can be used as an effective escape mechanism. It also has a slight knock-up effect, and this allows for you to run into pursuers to momentarily disable them.
As Powerball speeds up continuously after the initial cast, it's sometimes better to let it speed up in a brush before rolling at someone.
Flash can be used while in Powerball to jump across a minion wave to catch your opponent off-guard.
Powerball can hit stealthed champions such as Twitch, Shaco, Akali, or Evelynn, dealing damage and knocking them back. It will also work against a CamouflagedTeemo, knocking him out of stealth. This can be useful for chasing them if they go stealthed at low health.
You can use Powerball then use Teleport to be at a high speed when reaching your destination.
Puncturing Taunt can be used on enemies pushing your turret to make them attack you and causing the turret to attack them. It can also be used to take the focus off more squishy allies, allowing them to deal more damage than they would have had they been the focused target.
Puncturing Taunt can also be used to "pull" enemies towards your team as an enemy will be forced to get into attack range to hit you. This is more effective with melee champions whose attack range is shorter than ranged ones.
When using Tremors, you can use all your spells to keep enemies in range of this spell in order to maximize damage. This is possible because the ultimate is not channeled.
Tremors affects turrets, making Rammus a very good pusher, especially lategame when he can tank the turret for his team.
Backdooring is a simple matter because you can easily use Powerball to run away before enemies catch up.
Rammus can use Tremors while using Powerball, making it very useful for destroying towers or champions that are low on health and escaping.
Building armor is necessary to put Spiked Shell to good use. Having a lot of armor will still result in a large amount of damage. However, do not disregard building magic resistance, as your high armor stat means nothing to the enemy team's APmages. It can however be argued that building health will synergize better with the free armor and magic resistance provided by Defensive Ball Curl.
Atma's Impaler synergizes well with Spiked Shell, increasing his damage further while also providing armor.
Thornmail is a very effective item on Rammus, as it reflects damage from auto-attacks (which the enemy is forced to use during Puncturing Taunt) as well as stacks with the reflecting damage given during Defensive Ball Curl.
Rammus'sTremors and Powerball can deal massive damage with some ability power. This makes Zhonya's Hourglass a rather potent item as it also provides a large amount of armor.
Rammus is a strong jungler, with exceptional ganks. Powerball allows him to initiate ganks suddenly, and Puncturing Taunt is a strong CC ability with a fairly long duration.
Note that Rammus'sPowerball, whilst it still does damage, it has no crowd control effect on Baron Nashor or the Dragon. Also note that Puncturing Taunt now has absolutely no effect on Baron or Dragon (it will not reduce armor or force either to attack you). Both skills will still affect all other neutral creeps as normal.
Be aware that crowd control abilities will not stop Rammus'sPowerball while it is active, but will slow/stun/snare him in place, allowing you to potentially dodge the attack.
Rammus is an excellent counter to all AD carries due to his Defensive Ball Curl and tendency to build high armor. It is wise to have a mage or a hybrid champion (e.g. Jax or Akali) take him down.
Building a Last Whisper will penetrate his armor, allowing you to deal more damage to him.
If Rammus is building AP don't let your guard down, Powerball and Tremors have decent AP ratios and low cooldowns.