I'm going to do netflix as I use netflix already and I'll just create a new subscription.
One to avoid for sure though is Energy Plus. It seems they have a very bad record of increasing prices on people a few months after switching to them for electricity/gas. If you google them you'll find many people spent hundreds of dollars more over a year or two than if they had used their local utility company.
Some of their mileage sign up bonuses are very lucrative (8k-10k or so) which is fine if you then monitor your bill and cancel within the first few months if they overcharge you.
But in terms of the grand slam your ENTIRE grand slam bonus would hinge on you not cancelling, so you could end up paying hundreds of dollars more knowingly as they up to 110,000 US airways miles hostage.
I'd avoid that one like the plague.