Become a Prizefighter

Become a Prizefighter is a quest in Fallout 2.

Walkthrough
Beat all 4 contestants at boxing.

If you go into the Jungle Gym and talk to Stuart Little you can box. If you are female or have Strength lower than 6, you'll have to pass a relatively easy Speech check. You'll meet four increasingly difficult opponents: Joqq ($50, 500 xp), Pete McKneely ($50, 750 xp), Evan Holyfeld ($400, 1000 xp), and the Masticator ($1000, 2500 xp). This is assuming you get 50% of the winnings; with Speech 76% and Barter 76% you can get 75% instead. You also get kill xp for those boxers you manage to beat to death; this should happen some of the time and counts as a knockout. Other ways of winning include "normal" knockout (if you score a critical hit that knocks your opponent unconscious or if he himself manages a critical failure), technical knockout (if you make him flee), and points (if you somehow manage to make a fight last 12 full rounds and win the majority of them by landing more punches than your opponent). If you win four matches you get the Prizefighter reputation which lets you empty the gym lockers, makes you popular in New Reno and gives you a +5% bonus to your Unarmed skill.

Should you lose a fight, you must ask Little for a rematch immediately or you won't get another chance. You'll then go up against another boxer (your royalties will drop to 25%, but the xp is the same). You can only convince Little to give you one more chance (unless you exploit a bug), which means you can fight five matches in all, and there's a tempting reason to do that (see another note below).

Bugs

 * If you've won the game, Little's dialogue will always go as if you're talking to him for the first time, meaning you can ask about boxing, negotiate a deal and get your "first" match (though the game keeps track of how many opponents you have defeated). If you have still not won the game, you have to leave dialogue after losing a fight, talk to him again, ask for a rematch and fail a Speech check (which is impossible if you're at 100% or above). He will then let you box again. Note that the only reason for doing this is to up your resistances, which is a bit cheesy. In fact, knowing that you can raise them arbitrarily puts a damper on my desire to get that fifth bonus, since I usually have no problem taking advantage of limited glitches but have no interest in the unlimited ones.
 * If you lose by knockout there may be a bug that makes you lose the rematch before you even get to start fighting. This is because when combat ends directly after you score a critical failure that makes you lose your next turn, the game remembers that you have a lost turn coming up, and if that happens to be at the start of the next fight you lose again. Simply entering combat mode once in between the fights to get rid of this "debt" should take care of the matter (assuming you wouldn't rather reload after such an unfortunate occurrence).
 * In the unpatched version losing your ear could give you a bonus to your CH, because the command to change the stat was being used incorrectly. This bonus would be equal to your current CH minus one, except if this would take your new CH above 10 in which case nothing would happen.
 * At the beginning of each round starting with the second, after the ring girl appears and the other boxer runs towards you, there's a small window where you can press A to enter combat mode. You can use this extra round to attack your opponent, or you can use it to kill the ring girl. The latter changes nothing except that the ring girl will be lying in a pool of blood instead of walking. If you manage to kill your opponent in this combat round, you will be stuck forever inside the ring after the announcer makes a brief appearance. You can get an odd item - the Special Boxer Weapon, a useless sort of club - by killing the ring girl, then knocking a boxer unconscious on the same hex and looting his body before the combat round ends.