Pheeble Will

 is a quest in Fallout: New Vegas.

Quick walkthrough
Bighorner rancher Walter Phebus and his wife, Ethel Phebus have traveled to New Vegas on the trail of big-name rancher/robber baron Heck Gunderson. Walter seems bent on revenge after having some of his land taken by Heck in a shady deal.They can be found at the Strip near the Las Vegas Boulevard Station.

Detailed walkthrough
Initiate conversation with Walter Phebus and find that he is in New Vegas and has trailed Heck Gunderson to the Ultra-Luxe casino. Walter tells you his troubles, and requests that you to find out why Heck is visiting the casino. You may pass a Barter check of 70 to receive 400 caps for accepting this quest. Ethel, however, will attempt to get you to persuade her husband to let the matter go. (To accomplish Ethel's purpose, you need a perception of 7 and then must pass a Speech check of 75.)(This will end the quest with an EXP reward of 375.)

After speaking to Heck, accompanied by his bodyguard in the Ultra-Luxe casino, you find that he is attempting to make a food supply deal with the White Glove Society, and that his son, Ted Gunderson, is missing. This will initiate the quest Beyond the Beef. Upon informing Walter of Heck's troubles, Walter makes you an offer to take out both Gundersons. The reward can be increased to 500 caps for Ted if you pass a Barter check of 80 and 1000 caps for Heck with a Barter check of 90, or you may offer to just "take care" of them. There are a few ways to get rid of Heck:

Option 1:

One way to get Heck to a secluded area is to steal something from him and run to the penthouse door. He should follow you. When he gets there, go in the penthouse and run around the corner. Then let him get away from the door so he can't backtrack to escape.

Option 2:

Another (valid, but risky) option is to run into the Ultra-Luxe casino lobby, refuse to hand over your weapons, and kill everyone (though this will obviously lead to substantial drops in karma and White Glove Society reputation).

Option 3:

Completing Beyond the Beef by siding with Mortimer and framing Heck Gunderson with Ted's death will result in completing the conditions of both quests simultaneously.

NOTE: Another option if you want to kill Heck is to sneak in (requires 50 sneak skill) at least 2 throwing knives or a silenced .22 pistol or some other quiet holdout weapon and go to the left side of the room near the wall next to a plant and crouch where you should be hidden most of the time and use V.A.T.S. to kill him with headshots.

Bugs
If you bring Ted Gunderson to Heck Gunderson (while completing the quest Beyond the Beef) and talk to Heck Gunderson, then this quest will be failed, Walter and Ethel will disappear. Even if you kill Heck immediately.