Mozilla Firefox : SpiderMonkey, TraceMonkey (v3.5), JagerMonkey (v4), IonMonkey (v18), OdinMonkey (v22)
Google Chrome : V8
Opera : Futhark(v10.10), Carakan(10.50), V8 (v14)
Among all Google’s V8 is the fastest one and here is a little info about it :
It has the flexibility to be able to be used client or server side.
It can also be found in MongoDb (version 2), Node.js and many other powerful and popular applications.