ha ha well in that case im gonna have to change my list!
1. Armed security guards to protect my tanks
2. Deadly Lazar ray to vaporize algea
3. airline tubing
Lepisosteus beat me to it. Provded you already have all the basic essentials that are needed to maintain a aquarium. This would be my list.
1.Generator in case of power failure
2.Spare tank large enough to house monster fish due to fighting or breeding.
3.Some basic Meds in case of any parasite or bacterial infections brake out.