[...new Set(arr)]
.Object.values(arr.reduce((acc, n) => (acc[n] = n, acc), {}))
// или
Array.from(new Map(arr.map(n => [ n, n ])).values())
// или
arr.filter(function(n) {
return !(this[n] = this.hasOwnProperty(n));
}, {})
// или
arr.filter(((picked, n) => !picked.set(n, picked.has(n)).get(n)).bind(null, new Map))
// или
arr.filter((n, i, a) => i === a.indexOf(n))
// или
arr.reduce((acc, n) => (acc.includes(n) || acc.push(n), acc), [])