This isn't a new tactic, but it is a great tactic that I rarely see people use.Every character comes with at least one C4 charge.
You can easily land this on a vehicle by running upto a vehicle and aiming a little high as you run by.
The stealth Black Hand is great because you can hit a tank from behind with C4 then back up and start shooting.
You can even do this to enemy infantry.
I've been able to sneak up on players (mostly snipers not paying attention) and place C4 on them and run away and detonate.
You just have to aim a bit high (for their head usually) and it will stick to them.