Alright, so, here's the story: When I buy liquor to drink at home, I keep what I have pretty simple. I'll have a bottle of gin, a bottle of bourbon (and though I don't always get the same thing, it'll usually be one bottle at a time), some sweet and dry vermouth, occasionally some rum, and that's pretty much it most of the time.
Part of the reason is that in general I'm usually on a budget, part of the reason is that I don't entertain guests too often, maybe it's habit, but fundamentally, that's what I keep at home/drink regularly.
Anyhow, despite how simple that is, I know there are a tremendous number of interesting and exciting liqueurs out there, some of which I've tried or had in cocktails but never bought a full bottle of, plenty of which I've never tried, and I'm sure plenty of which I've never even heard of. So I'm thinking that whenever I get around to restocking, I'll try to pick up a bottle or two of something different.
So, I suppose I'm asking for recommendations/suggestions. I'm sure I'll be using whatever I get to make cocktails, so ideally I'm looking for something that can work with gin, whiskey and vermouth (and occasionally rum?) in some capacity. And I guess versatility would be good (I know, it's a bit much to ask for given how little I actually have to work with, but at the same time, I wouldn't want to get the kind of liqueur that can be used to make only 2 drinks in the whole world, with of them also requiring aquavit, applejack, chambord, and some sort of syrup that hasn't been sold in America for the past 50 years.)
Also, I'm not opposed to liqueurs that can be consumed straight.
In terms of flavors and such, I'm not too picky; I think herbal is a good property, although I like lots of things. I'm comfortable with bitter liqueurs too (like Campari, Italian aperitifs, etc.), but there isn't any particular type of liqueur I'd rule out, other than overly sweet or candy-like ones (I can even enjoy those, although that's really not what I'm looking for right now).
So, since I'll be thinking about this for a while before I buy anything, are there any suggestions anyone can offer? Any advice would be appreciated.