Satchel Charges
The Satchel Bomb is a remotely-detonated explosive from GTA San Andreas. When charges are planted, the player gains a detonator in an additional weapon slot, and by firing the detonator the bombs explode. The satchel bombs can be detonated from any distance, and with any time delay, assuming they still exist.
This is another non-standard piece of equipment which doesn't replace anything in the equipment slot. There's not too much to it either. You only get the remote detonator with the remote explosives listed above, and use it to, well, detonate them by switching to this item and pressing circle. After the bombs are used up, the detonator is discarded from your inventory.
The potential for mischief with these things is only limited by the imagination, well, and the CPU's ability to remember where they're at, but, still... On a mission where you have to ambush and kill a ped or destroy their car? Try figuring out where they'll pass, and set up a nice booby trap for them! Or if you suspect the next corner you're to walk around has enemies waiting for you, throw down a few bombs, run in, and lure them out to an explosive doom. Any way you look at it, there's much fun to be had here.
Even in the lackluster local-multiplayer component to GTA:SA, you can stick satchel charges to the other player and blow them up.