i dont know what you guys consider a combo...maybe i can set it straight; a combo in brawl is any sequence of moves which, once started, usually cannot be stopped until completed. i write "usually" because there are always exceptions (i.e. the weight of the opposing character, the damage he/she has suffered, etc--thus, the percentage range during which a given combo is possible).
combos i use-
bair>bair>ftilt = 36% (if they trip, then a dash-attack or down-b. used at low percents, roughly 0%-15%, depending on opponent size)
dtilt>dsmash>uptilt>upsmash=56% (very efficient combo at low percent, but becomes less effective and eventually impossible at mid percents))
d-throw>ftilt = 17% (good quick starting/follow-up combo, low/mid percents, about 0%-40%)
(on stage ledge) bair>dair usually = ko (best use of DK's dair meteor smash, but I found it difficult to master...it's amazing once you do. Effective 0%-30%)
bair>bair>uptilt>bair>bair = 66% (excellent starting combo, but only usable at 0%)
dtilt(trip)>forward-b>down-b = 46%-32% (a personal favorite, but suffers decreased effectiveness past 30%. 46% = opponent < 30%, 32% = opponent has 30% or greater)
dtilt(trip)>foward-b>up-b = 50%-54% (perhaps DK's best combo, due to its large percentage range, and it's increased effectiveness at mid-percents. 0%-55%)
Mithx mentioned juggling...which is not really comboing. While i agree that it is extremely effective against many characters, there's no required skill. Also, DK's dash attack should only be used at the end of a combo, so as to eliminate it's long recovery period.
