Honestly, It Depends on the level and moves. I personally love jolteon. Your 6th Pokemon Can Be HoOh.
lv.36.
get an eevee and evolve it into a thunderstone
The only way to get a Feraligatr is to pick Tododile as your starter Pokemon and evolve him into a Croconaw at level 18 and finally into a Feraligatr at level 30. You can also trade from other games to get a Feraligatr.
Feraligatr learns the moves double head hit, sonic boom boom and slap attack with lightening.
The easiest way to "see" a Feraligatr is to battle your Rival only if you chose Cyndaquil as your Starter.
Mount Silver is the best place to train feraligatr Lv 42 and ampharos lv 37.
Lucas has a Monferno.
Monferno has no specific partner pokemon.
Feraligatr is a Water type pokemon.
Monferno is a Fire and Fighting type pokemon.
Well for me, I got my brother (he plays pearl) to trade me a chimchar egg. Then I hatched it, and evolved my chimchar twice. Tip: Chimchar to monferno= lvl 16. Monferno to Infernape= lvl 36.
You cannot get Chimchar, Monferno, or Infernape anywhere in HeartGold or SoulSilver. You will have to trade over a Chimchar from Diamond, Pearl, or Platinum.