Pi-calculus solves consensus
Dolev, Dwork and Stockmeyer in 1987 examined the variations of asynchronous message-passing models where consensus is solvable . They examined the axes of processor synchrony (can processors sleep indefinitely or is their sleep bounded?), network synchrony (are messages received in a bounded number of steps after being sent?) and message-order synchrony (are messages on a channel received in the order they're sent?). The result was that processor synchrony doesn't help (1-resilient consensus is unsolvable whether processors are synchronous or not) but either of the other two parameters alone makes the difference between no fault-tolerant consensus and n-resilient consensus (any number of process failures can be tolerated).
The (synchronous, or classic) pi-calculus is a "model of concurrency" where messages are rendezvous points: messages are received right when they're sent and thus in order. This implies that pi-calculus can solve n-resilient consensus.
In case you're not convinced, here's a pi-calculus expression that solves it*.
* For pedants: my solution is only (n–2)-resilient: it deadlocks if only one process is non-faulty.
UPDATE: C. Palamidessi had shown that synchronous pi-calculus can solve consensus and that asynchronous pi-calculus cannot . Wischik and Wischik have a protocol for synchronous rendezvous , which suggests that pi-calculus is achievable purely given the right primitives, and probabilistically achievable in any case.