Although what the others have said is 100% true regarding needing more info on parameters, here are a few specific firearms to consider:
Revolver:
If primarily home defense (HD):
- 4" S&W 7 shot 686 .357
If mix of HD and carry self defense (SD),
- 3" version of same 686 or--easier yet to carry--discontinued Smith 66 or 65LS ("Lady Smith")--both .357. Don't let the name on the LS fool you: best combo of features you can get in a mixed-duty revolver, IM0. These are 6 shot.
The 66 is adjustable sight, a consideration if spending a lot of time at the range or field (hunting). Otherwise, the 65LS is a fixed sight which is fine for home and smoother holstering for carry duty. The 3" length is a great one. It's a mystery why S&W made so few. They provide a better sight radius and recoil (muzzle flip) control than the 2"+/- snubs, and easier carry than the 4 inchers. Three-inch 66s are not growing on trees out there. The 65LS in particular is getting to be a rare critter and pricey; worth it if you can find one however--the most "investment" worthy of the bunch, again IMO.
The only "downside" of the discontinued K frames (65, 66 etc)--versus the slightly larger "L" frame 686 model--is that they were not designed for a steady diet of today's popular, hot 125 grain .357 self-defense loads. They can take a variety of 158s all day long, many of which are fine for SD....and as mentioned below regarding carry options, most folks shoot .38s most of the time in them anyway, whether for range/target practice or in-home self defense...so the 125 grain limitation is, usually, a moot issue. As always, you can't get something for nothing. With the 686, you get a slightly larger, heavier gun that is--along with the penalty of that additional size/weight--is more "capable." If that size and weight are not a concern, there's your answer--and certainly an easier one in terms of actually finding one to suit your needs.
If primarily carry or concealed carry (CCW):
- Smith 60 or Ruger SP101 .357, and shoot primarily .38 (target) or .38+P (defense) loads most of the time anyway--especially in the home. These are 5 shot.
- Colt D-frame snubs: long discontinued, but the famous Detective Special (.38 Special) and Cobra (.357) are rare small frame combined with full 6 shot. The later (70s-early 80s?) models with full ejector shroud are worthy for SD consideration. The only small frame 6 shots currently being made in the .38/.357 class are Taurus-owned Rossi (.357) and Taurus itself (.38), and while there are some good reports on, others are mixed...and so there is less consensus yet on these to make a recommendation for your "investment."
Semi-auto:
Home-oriented defense (HD)
- H&K (Hechler & Koch) 9mm or .40S&W (variety of models, USP is one to look at)
-SIG 9mm or .40 Auto (variety of models)
The above autos are pricey, but since you seem willing to spend--they're "investment" worthy.
HD/SD/Carry combinations
- Above H&K 9 or 40 reg and compact
- Springfield 9 or 40 XDM reg and compact
- S&W M&P reg and compact 9 or 40
- Beretta PX4 Storm 9 or 40
- Walther 9 and 40
- CZ 75/85, P series 9 and 40.
The auto world in particular is a complex one in terms of preferences, features, prices. Once we know those more detailed parameters of your needs/intended use, folks can weigh in on desirable or undesirable features (esp the semi-autos), such as safety vs no safety, decocker vs not, DA or DA/SA vs SA. Most manufacturers of autos have a number of models with a mix of features, depending on what operating characteristics you (think you) want.
(EDITED later for additions)