HO leads need to do 4 things: set up hazards, provide free turns, and keep things from setting up on them, all while making sure that they don't create double switches.
There are only a few types of leads I would consider: Dual Screens + SR, Encore + SR, Trick + SR
All of these leads give free turns offensively with SR and give free turns defensively with their support moves, while making it difficult for them to be set up on.
DS + SR is done best by Azelf, plain and simple. access to taunt is awesome, especially with its speed. it allows it to be impervious to status from slower users. Most leads you find will be weak to status, unless they use lum berry or have fake out. lum berry means no sash/light clay. Azelf's fast taunt is really the draw. It keeps it from being setup bait, which uxie and zong wish they could do. Who cares if Zong/Uxie can come in twice when they are slept or set up on and don't really have any improved lead matchups? The reason why people use Azelf is that Dual-Screening is the longest lasting setup, giving you more extra turns that anything else, and Azelf is the best at it.
Encore + SR is pretty exclusive. As far as I know, only Infernape, Clefable, and Shuckle get it. Infernape is the obvious inclusion for an offensive team. He draws in bulky waters, can kill opposing leads, and also is not a common user of encore, with fake out being more common. This gives him the element of surprise. drawing in earthquake, psychic and waterfall is great, since tar/gross or mence/gyara eat those up.
Clefable could be decent on some HO team, because it gets dual screens, sr, trick and encore, and drawing in fighting moves gives LO gar a turn of fun. It also is impervious to status and weather breaking the sash. If you need to swtich, it will also still have the sash after coming in on SR.
Shuckle is probably to be avoided, as he will probably be uturned to death or something, though he does draw pretty much the same stuff as ape.
Trick/Switcheroo + SR is not uncommon at all. Azelf, Uxie, Celebi, Mespirit, Jirachi, Clefable (again :D), and probably some other stuff that I can't be bothered to find. I have never used on of these. Maybe someone else can tell you about them. There are three problems here that I can see. First of all, you just gave them a revenge killer. Second of all, you are setup baiting after tricking. Third of all, if you are against another trick scarf lead, you will be setup bait for something later. The good news is that you will cripple something, meaning free sr, or get your self killed, allowing for a free switchin encore-style.
Offensive leads are sort of not as good. They provide no extra free turns of setup that may be needed to plow through counters. The biggest problem is that adding attacking moves means that you are either missing out on SR or extra coverage. If you are missing extra coverage, you will probably be set up on. Missing SR has obvious disadvantages (I have missed a lot of LO gross kos because of not having them up). If they have SR + perfect coverage then more power to them. I haven't found many (read: any) that can also beat common leads in addition to these things.
All in all, Azelf accomplishes the 4 things that leads are supposed to do the best.