SmashCAP2 - Type Submission
Fire / Ice
tl;dr: this typing is incredibly bad defensively and incredibly good offensively.
Defensive
Resistances: Ice (x2), Grass, Bug
Weaknesses: Ground, Rock (x2), Water, Fighting
Defensively, this Pokemon is a wreck. Bug is fairly uncommon attacking types; switching into resisted attacks will be difficult. Grass is a move type that might only be seen once once on a team, usually solely for Swampert. The double Ice weakness, however, is more useful. Ice attacks are on all teams because they check the beasts that are Salamence and Gliscor. It would be fairly easy to switch into Scarf Jirachi's Ice Punch, Weavile and Mamoswine's Ice Shard, Starmie's Ice Beam... the list goes on and on.
Weaknesses to Ground, Rock, Water, and Fighting are all quite horrible. Ground, in the form of Earthquake, is the most commonly used move in the game. Stealth Rock cuts this Pokémon's HP in half upon switching in; Rapid Spin support is very useful. Any other Rock attacks will OHKO this Pokémon. Water, found in Surf and Waterfall, makes up roughly 15% of all offensive attacks. A Fighting weakness is also bad. Close Combat and Superpower both hover between 5 and 6% of all used moves.
The faint light that shines behind these weaknesses are its teammates. Many Pokémon are immune to Ground and Fighting attacks. Vaporeon stands alone as an OU Pokémon who is immune to Water; Quagsire and Poliwrath are two less common Water Absorbent Pokémon. As previously stated, Stealth Rocks can be Rapid Spun away.
Offensive
Super-effective: Bug, Grass, Ice, Steel, Dragon, Flying, Ground (one or both)
Ineffective: Fire, Ice, Water (both)
Offensively, the Fire / Ice typing is simply amazing. Steel, Flying, and Dragon are all very common types, and are all hit super-effectively. Less common, but still often seen in OU, are the Ground and Bug Pokémon. The Pokemon who resist the offensive combination essentially boils down to Heatran and bulky waters. Ice Pokémon are rarely seen and defensively frail. The glass cannon that is Infernape is also excluded. Bulky Waters could be dealt with by moves such as Thunderpunch, Thunderbolt, Leaf Blade, or Hidden Power. Scarf Heatran has a ridiculous weakness in that being locked into a move is very bad because its common move's typings are offensively weak. Non-Scarf Heatran are easily outsped and OHKOed by the likes of Infernape, Flygon, and Swampert.
Going even more in-depth, this Pokémon has "anti-metagame" merits. Scizor, Salamence, Latias, Jirachi, and Metagross are are hit super-effectively by this Pokémon's STAB attacks. Those who aren't harmed by a Fire / Ice combination, such as Tyranitar, Swampert, and Gyarados, are maimed by Grass or Electric attacks. Then there are Pokémon like Gengar and Infernape who are OHKOed by almost anything.