Given the constraints of an interesting, high-damage, revenant at level 3. We first must discard the striker classes. While the idea of "striker" generally means high-damage, there are other ways to achieve high damage without it.
While it is always preferable to optimize a group over an individual, such that members can support each other, it sounds like your group has most of the "support" roles covered.
At level 3, most of the shennanigans possible with a revenant are quite limited. Getting access to half-elf's Dilettante is therefore contraindicated.
The most obvious "fun" build is one that maintains control of the battlefield while outside of their turn.
A revenant is +2 Con, +2 Dex/Cha. The "highest damage output" is easily a fire elementalist. At level 6, the top of the DPR king charts are dominated by thieves and rogues, especially ones that can trivially riposte.
That is, however, outside the scope of this effort due to the "interesting" restrictions.
In a trivial sense, we'll make you do damage by applying the charge-chassis. It's "boring" in a sense, but when combined with other features, it should make "who do I charge?" a meaningful choice to make every round.
At level 3, the charge chassis (in a non-thief) consists of: Melee basic attack, suprising charge +1[W] with CA (feat), Avalange hammer +1[W] on charge, bracers of mighty striking, +2 damage and the badge of the beserker.
While it would be a tempting trap to go dwarf as past-life race to pick up the ever cheesy dwarven weapon training, the fact that the revenant is not a strength-primary should be foremost in our minds.
Base class: knight. The knight (especially in low-mid heroic) is an exceptional defender as Sohum has shown in my weekly online game. We go revenant knight, past race tiefling. Tiefling is critical for us because the feat support is exceptional.
We must take a multiclass paladin feat and wrath of the crimson legion. This build would flow far more smoothly as a dwarf, but the revenant presents its own unique opportunities. The feats you will want in the future are: Weapon Proficiency(Mordenkrad), Two-handed weapon expertise, past-soul (tiefling) and Suprising charge.
For now, however, you have a knight that uses charisma as their primary stat, with dex as secondary (to qualify for surprising charge), wielding a maul. Every time she charges an enemy, you'll attack for 4d6+static modifiers + slow, have your knightly aura up to prevent movement (and your default MBA is a scary 2d6+static). This will make you the centre of attention, force you to pay attention every turn, as the aura violation is an opportunity attack, not interrupt, and will be a simple but tactically-enjoyable build.
Actual CBuilder paste coming later.