Unique champion takedowns grant permanent out of combat MS.
Rammus is all about engaging with the CC of his [Q] and [E] and the taunt should last long enough to keep your target in the explosion radius.
Bone Plating makes you extra durable in those early game ganks allowing you to go toe-to-toe with any apposing duo in a 2v2.
Rammus benefits massively from both Armor and Magic resist, scaling his [W] to make him an unkillable machine.
Rammus' biggest counters are CC and slows applied to him while rolling in. Unflinching allows you sure up some of those weaknesses.
Rammus' ability to repeatedly Slow/CC enemy champions with [Q], [E], and [R] allows him to proc bonus Cheap Shot True Damage in nearly every skirmish several times, granting you the extra bit of damage for any kill.
Relentless Hunter's stacking Movement Speed combined with your [Q] allows you to get to any fight or skirmish on the map at the drop of a hat.