Like I commented, it seems strange you want another Pokemon not weak to Fire and Fighting when you already have Jellicent?
Do you want a Pokemon that's resistant to those types or just not weak to those types, i.e. damaged neutrally? I don't think there's any typing that would make a Pokemon resistant to all those types. In any case:
Starmie @ Leftovers
Ability: Natural Cure
EVs: 252 Hp, 252 Speed, 4 Def
- Rapid Spin
- Scald/ Surf
While Starmie doesn't make the best physical wall, it will remove threats like Gengar (it will out speed it with max Speed EVs and positive nature) with Psyshock. Psyshock also allows it to deal more damage to Blissey. Also fills your Rapid Spinner role if you don't have one already.
Slowbro @ Leftovers
EVs: 252 HP, 252 Def, 4 Sp. Atk
- Slack Off
- Ice Beam/ Thunder Wave
Slowbro makes a good physically defensive Pokemon, what with Regenerator and already high Def, along with a reliable method of recovery. But like Starmie, it'd be adding another Grass/ Electric weakeness on the team.
Tyranitar @ Leftovers
Ability: Sand Stream
EVs: 252 Hp, 80 Atk, 180 Def
Nature: Bold/ Careful
- Low Kick/ Superpower
- Stealth Rock/ Stone Edge
Tyranitar is resistant to Flying, Fire and immune to Psychic; while it has a x4 weakness to Fighting, you say you already have Jellicent on your team, which means you can successfully wall Fighting moves as well. Jellicent also manages to take the Water, Steel and Bug hits as well.
If you really want, you can give Tyranitar Chople Berry, but then you forfeit leftovers recovery.