Okay, just to play devil's advocate, here's a bit of Olde English from around 1000 AD (taken from the Wikipedia article). Anyone who is really serious about grammar mistakes should probably speak primarily in Olde English, since so much of the evolution of the English language has been by grammatical "mistakes"

Cnut cyning gret his arcebiscopas and his leod-biscopas and Þurcyl eorl and ealle his eorlas and ealne his þeodscype, twelfhynde and twyhynde, gehadode and læwede, on Englalande freondlice.
Yes, that IS English!

JonV