"Fallout 4" gives you many freedoms: to explore, to build settlements, to stab sleeping raiders in the middle of the night. But it also gives you the freedom to do some pretty dumb things, which more often than not culminate in embarrassing deaths.
1. Your own grenade. Throwable explosives, whether ordinary fragmentation grenades, fiery molotov cocktails, or space-age cryogenic grenades are some of the best tools you’ll have available. But the throwing arc is a little weaker and less accurate than you might be used to. You may mistakenly lob a bundle of boom at a door frame -- or the back of your partner’s head -- which will have the adverse effect of leaving you, wasteland wanderer, slightly dead. “Bad grenade toss” won’t look good in an epitaph.
2. Flanked by a weak enemy. As you start to gain levels and pick up a few decent weapons, your confidence in your survival skills will grow. So when confronted with a pack of enemies, you may ignore those far below your level while you handle the “real” threats...only to be bitten in the back by an attack dog or Feral Ghoul you could have picked off in seconds. Ah, hubris.
3. Walking into a mine in the middle of the street. If you don’t have a particularly high Perception rating (or you don’t spam the VATS button while exploring), you’re going to run into many of the random mines littered around the wastelands. Sometimes these are well-hidden underneath debris, but others are right underfoot and you won’t notice them until the warning alert wails. Which is really more of a statement than a suggestion, since you won’t be able to escape the blast radius in time. Then your leg gets blown off by the mine you should have seen just laying around.
4. Aggravating a Deathclaw by shooting it at close range. Deathclaws are formidable -- this is understood. You can run into these walking embodiments of Hell even when you’re barely strong enough to kill Radroaches, and they’ll gladly kill you again and again. Deathclaws require patience and planning to take down (unless you bring along some heavy weaponry like the Fat Man), so walking up to one armed with nothing but a pistol and a backpack full of dreams is pretty high on the list of bad decisions.
5. Soaking in radioactive areas. Radiation is literally everywhere in The Commonwealth. Normally this isn’t that much of a problem, since there’s an assortment of anti-radiation drugs to combat radiation poisoning (not to mention the helpful Doctor Sun, who heals you for a fee). But you can still die from exposure if you’re not paying attention to your health bar. Or if you do something especially ill-advised, like walk straight into the Glowing Sea, a place dominated by a perpetual radiation storm. Equipping your power armor will stave off most radiation, but you have the option to walk in unprotected. Poor choice.
6. Stealing / lockpicking in plain sight without a high sneak score. As in other big Bethesda games, "Fallout 4" allows you to pick pockets as well as the locks on pretty much anything, all in the name of free stuff. If you have a high Perception and sneak score, you can do this mostly undetected (even in the open), but without those you’re basically screaming “I’m a thief” to anyone nearby. Try this in populated areas like Goodneighbor or Diamond City, and you’ll find yourself very quickly and severely punished by the local guard.
7. Exiting power armor without checking your surroundings. As previously mentioned, power armor is a very useful thing to have. But it requires a rather rare external power source, and it does limit some of your mobility. Eventually you’ll have to abandon it, which you do by climbing out of the back -- where an enemy could be waiting to blindside you. Or you could be unknowingly backed against a cliff edge, which will result in you, quite ridiculously falling to your untimely demise.