Boxer briefs. I had a thread on this topic a while back, and the BB’s were clearly superior.
Low rise briefs or trunks. I just like the way they look better than boxers or boxerbriefs.
By which I mean the shorts have a longer lifespan, not that they make anything look longer.
Briefs, all my life. I’m a creature of habit, I guess. Never worn a boxer and can’t even grasp how they are suppose to work. I like the sling supporting the bits that would otherwise get crushed when I sit down. The only other type of underwear I wear is a jock for exercise, because it does an even better job of getting everything out of the way of my legs.
Boxer briefs.
Briefs are uncomfortable (my boys need a little room down there). Plus I think of briefs (particularly the tighty-whitey kind) as what children wear. I think a man looks ridiculous in them.
(And it’s not just me. I loved the director’s commentary on one of my Simpsons DVDs where Matt Groening was discussing how The Simpsons was one of the first comedy shows to show men in underwear as wearing briefs. The reason? Briefs are inherently funnier.)
Boxers are clownish. I associate them with my high school days. Plus they aren’t terribly comfortable - they ride up your leg.
Boxer briefs are the perfect hybrid. They look good. They feel good.
Word, homie. 
Briefs for daily wear, boxers if I’m going to be seen. Like any article of clothing, you buy what fits you. If they feel too tight, they are.
String-bikini briefs.
I was raised wearing briefs. Always thought boxers were a bit “clownish”. (Mentioned above. Good description.) In USMC boot camp I conformed to wearing boxers for the first time in my life. Many derogatory expressions. It felt like wearing pajamas under my clothes. Too loose, twisted around easily, and it seemed like the entire backside bunched up into my ass-crack.
I do this quite often. Well, I never wear briefs, but I do like boxer briefs on a working day. I spend all day sitting at a desk and they’re better from a comfort POV. Aesthetically, I prefer boxers, though.
Now that I remember, some of my male relatives have that habit… Briefs for work, boxers to lounge around the house.
In the case of my friend, though, I couldn’t really identify a pattern other than “It must be the first piece of clean underwear he grabbed”. I didn’t care. 
Another vote for boxer briefs.
TMI???
In my opinion, boxers are almost useless. For me, pretty much the entire point of underwear is to keep everything from sticking together, especially when it’s warm. It’s a free country, but I honestly don’t get boxers, unless I’m going to be parading around without my pants for some reason, and that’s not going to happen.
I grew up wearing briefs, so they’re what I’m used to. I’d feel like I wasn’t wearing any underwear at all in boxers.
I tried boxers once a few years back. After an hour of work, I had to tell my boss I was going home to change my underwear. I definitely prefer the secure feeling of briefs… you can jump around and climb over things and there is no flopping.
As for style, I get colored Hanes.
Manties, sweetie. Manties.
Casserole, eh? Maybe you and I should, you know, get together sometime.
Usually none at all, I have a couple boxerbriefs, regular briefs for the gym and a few pairs of…well other.
In my thread, one of the responders described the experience as his naughty bits feeling “lovingly cupped”. That sold me right there.
BTW, boxers are fine if that is all that I am wearing, such as in my sleepwear. But they don’t provide adequate support/containment when I am clothed, as a result of which the center seam in a pair of pants (especially non-gangsta-rapper jeans) may make a decision regarding naughty bit allocation that can be rather painful, pending a potentionally embarrassing readjustment of said naughty bits.*
To the OP: a very nice Christmas/birthday/whatever present might be some high-end boxer briefs.
*I find briefs entirely too suffocating anymore.
Tighty-whiteys. I tried boxers a few times - can’t stand the flopping around. I have some boxer-briefs that I wear sometimes (when the briefs supply runs low). I kind of like them but they don’t seem to fit across my ass right. Like my ass is too big in proportion to my front (a sad thought that I don’t need pressed home by my underpants.)
Boxer briefs here. I have one or two boxers but they are used mostly when sleeping.