Opinions on flashlights, what kinds, and how to use them best in tactical situations, are as varied as weapons themselves. In reading the OP, I don't think s/he expected that much strong opinion on the question.
I love flashlights. Have multiple ones around the house and in the Jeep. I have to carry one on my duty belt for the armored car company I work for, and after a little more than 4 years of trying different ones, I finally settled on a
Fenix TK21. I prefer lights that accept rechargeable 18650 batteries. Cycle-life is quite impressive, and on that particular light, when power gets low, the light automatically switches to the next lower setting instead of just shutting down. The TK21 is a medium-high output light at around 460 lumens on high, which is about 4 times as bright as you need for home use, but it also has four levels and remembers the last setting used, so it's still useful at home. My duty belt stays in a locker at work though, so....
I keep an
Olight T-20 Military by the bedside. (Link goes to "Tactical" model - "Military" may be discontinued, but only slight differences between them.) As of this writing, that link has a great sale price. This light maxes out at 220 lumens with memory of last-used level. I keep mine on the low or medium setting to conserve batteries as much as anything. This makes a good rifle or shotgun light too. Very lightweight, pressure-switch accessory available, and the one I have has stood up to thousands of rounds sent downrange with it mounted on my 5.56 rifle.
I agree with what kelcarry said about the use of a light giving away your own position as much as illuminating the area in front of the light. A light is a tool just like a gun. You have to train with it and know ahead of time what situations call for its usage and which call for staying dark. I have a S&W 4563TSW with a Streamlight TLR-2 attached, but I train myself not to immediately use either the light or laser. It gives an intruder a target, certainly, at the very least, a general direction to shoot at, so I would only use either/both functions if I absolutely needed them. The TLR-2 has easily-manipulated controls to switch between functions, but that is another thing you have to train extensively with before counting on either the tool or yourself in a tactical situation.
Bottom line, train, train, train, and when you think you've trained enough, start over and refresh your training. Weapon or tac-light, neither make you safer if you don't know how/when to use them.
Blues