I'm on record in any number of venues saying that Altbier is the perfect beer style. Not only do I love brewing and drinking it for its showcase-like approach to featuring malt and hops in a highly-consumable (if not quite "session") strength, but I like that I can use it as a nearly-year-round "house" beer style. Once in a while, though, you want to push the envelope a bit more: celebrate a special occasion, commemorate an anniversary, show off at an event, etc. On those days, I'll reach for a recipe for a style that doesn't even exist in the BJCP Guidelines: the "Sticke" (or "secret") Altbier.
The 2015 revision added a panoply of IPA and Historical and other specialty styles, but strangely collapsed all Altbiers into one category (and, for that matter, indicated explicitly that sticke altbiers didn't belong in that category, without indicating where they should be entered - but I digress…). I guess there's always the good old "Experimental Beer" sub-category, but it feels odd in a style with such a long history.
You'll have to hunt down your own category for entry, but one thing you won't need to do is wonder why you brewed this style in the first place. It takes everything I love about the Altbier and turns up the volume, and while that's not really something you need every day it certainly makes for a great change of pace!