Question

Again, strategy.

http://pokemondb.net/pokebase/47910/what-pokemon-have-a-double-resistance-to-water

Answer 1

Kingdra, Palkia, Corsola, Omanyte, Omastar, Kabuto, Kabutops, Tirtouga, Carracosta, Magcargo, Reshiram, and Relicanth. As you can see most are water types. It is worth noting that all Pokemon with Flash-fire are immune to Fire.

Comments

I didn't know about the flash-fire ability.  Whups.

Answer 2

Fire-Rock pokemon that have a 2x resistance:

Magcargo

Fire-Dragon pokemon that have a 2x resistance:

Reshiram

Water-Rock pokemon that have a 2x resistance:

Omanyte
Omastar
Kabuto
Kabutops
Corsola
Relicanth
Tirtouga
Carracosta

Water-Dragon pokemon that have a 2x resistance:

Kingdra
Palkia

Sources: Pokemon Database and Serebii