This is a term that can be used open-endedly, but origionated from rpgs where different combat syatems are used. In such rpgs favorable combat can be used by taking advantage of a unit strong in
one combat syatem but weak in another by forcing them to use the "unfavorable" combat
system. Some of examples of this are forcing an ubermage to attack you with a staff by attacking it with a meele unit in "the battle for wesnoth", attacking a
lance using unit with an
axe usng unit in "fire emblem", or going out of your way to use a morningstar instead of a greatsword in "dungeons and dragons" because a particular
monster is weak against blungeoning and/or peircing damage but ressistant against slashing even though the sword would do more natural damage.
In the end, the uses of flavoable combat include but are not limited to making
fun of someone talking about combat benefits, or describe battle in an interestin,
funny way.