賭 (TO, kake, ka(keru): to wager, bet, risk, stake, gamble)
This kanji is non-Jōyō. A shell (貝) and a person (者) suggest a shell game or gambling! That’s half right; 貝 means “money” here, but 者 is a substitute for 射 (to shoot). Shooting money? Somehow this kanji originally meant “to bet money on something.”
奮 (FUN, furu(u): to be excited, stir)
When it comes to the meaning of this kanji, the on-yomi could serve as a memory trick; “fun” and “excitement” aren’t so far apart.
We need to magnify this character to see its parts:
奮
The top component results from a miscopying of 衣, “clothing.” This combined with 隹 (bird) and 田 (field) to mean “clothing flapping like a bird in flight.” The character originally meant “birds taking off from a field with much flapping.” Not quite my idea of excitement, but then I’m not a bird!
闘 (TŌ, araso(u), tataka(u): to fight, war)
The kun-yomi araso(u) is homophonous with that of 争 (SŌ, araso(u): to fight). The other kun-yomi of 闘, tataka(u), is the same as that of 戦 (SEN, tataka(u): war). Put those two kanji together backward, and you get 戦争 (sensō: war, battle + to argue), which means the same as 闘. Mere coincidence or evidence of a deep, tangled plot by someone somewhere? You decide.