Researching another post, I tried to include a link to the Platinum Card from American Express Exclusively for Mercedes-Benz because it was the best personal sign up bonus for Membership Rewards at 50,000 Membership Rewards for spending $3k in three months.
If the Mercedes-Benz version of the card is dead, then the best Platinum card offers is the standard offer of 25,000 Membership Rewards after spending $2k in three months.
Sure there is a $450 annual fee–the Mercedes card had a $475 annual fee–but you can get easily more than $500 in statement credits plus worldwide airport lounge access plus Starwood elite status by holding the card. See Get the Most out of Your American Express Platinum Card for full details on how to activate all those benefits in a three minute phone call.
Ideally I’m wrong and the Mercedes AMEX Platinum is still available, but I did search around and couldn’t find a link to it anywhere. If you have one, please share it in the comments!