In my 36 gallon I have about 3/4 Stony River brand black sand combined with about 1/4 black gravel.
In my 20 gallon I have very fine, Lowe's playsand that looks awesome but since it's so fine, it tends to get sucked into the filter more than others. It also has some shiny mica looking bits to it which look cool but I'm not sure that's good for the fish.
In my son's 55 gallon we have a combination of that Lowe's type playsand with Home Depot playsand which doesn't look as nice, but it also doesn't get blown around the tank as easily as the Lowe's type. It might be the best combination though cost wise.
But, I still love the look of the black sand with the plants.................