....for hunting,target shooting, big game,small game.....etc.
It was my first caliber ever and I've always kept one or two over the years even while expanding / experimenting / hunting with other calibers like the .40/.50/.54/.58/.62. I think the .45cal is an inherently accurate caliber that offers a lot of flexibility and unless long distances / really big game are routinely involved, they're hard to beat as a general purpose caliber IMO.
TARGETS...depending on the variety of targets, distances shot, and wind conditions, I personally think the .45cal is an excellent choice to cover the full spectrum with accuracy. However, the .40cal is an outstanding one for most of those situations as well. What the .45 brings to the table is greater flexibility to do other things, particularly if a one or first caliber gun is being considered.
HUNTING...the .45cal excellent for small game like groundhogs/coyotes, and for squirrels/rabbits with throttled back 30grns powder charges. However big game would need to be better defined...the .45cal has been good for me hunting eastern whitetails but the relatively small / light ball dicates that distance always be a serious part of the equation. For typical woods shots here in the east, the .45cal has gotten the job done for me at least to 60 yards. It would not be my first choice if 100 yard shots were the norm or for bigger size game like mule deer , elk, etc. The .50cal could be excellent as a one or first caliber choice in that regard...also great on targets, and throttled back powder charges still work fine for small game.
Additional thoughts on the .40cal:
For most distances and conditions I also think the .40cal is an excellent caliber for targets and small game but the tiny 92grn ball gives up a lot for big game. There will always be references to deer being taken with the little .40cal...just like deer have been taken with a .22cal...but neither are classified as big game calibers because they're not the best choice when distance, bones, and hunting conditions are all factored in. So if a one or first caliber choice is part of your question, the choice should probably tilt heavily towards a larger caliber...really have to weigh things like what you'll really use it for and if it'll be the only caliber you'll have.
As one other perspective...for my type of range shooting plus hunting here in NC as I prepare for retirement, I've been selling off most of various rifles and smoothbores accumulated over the years with the goal of ending up with one small caliber rifle (.45cal), one big caliber rifle (.58cal) and one smoothbore (.20ga).
Others mileage may vary of course...