this poke is pretty much very limited in testing so ajustments can be made to it, was basically trying to make a gimmick moveset which could spring a few surprises
Moveset Name: bellydrum drainpuncher
Move 1: Belly Drum
Move 2: Drain punch
Move 3: Aqua Tail
Move 4: yawn/trick room/zen headbutt/rain dance
Item: leftovers/shell bell
Ability: own tempo
Nature(s): Adamant
EVs: 252 HP / 252 Atk / 4 spdef
witha slow speed,this poke isnt going to set the world on fire by fast sweeping, however exploting the situation of having a pokemon known for stalling and using special attacks you have a shock tactic in a physical sweeper with access to a combination of great defences and belly drum you have a great, if limited, physical sweeper, and with access to drain punch to back up your relative bulk it still keeps its walling status, throw in a shell bell and reep the effects of a few extra % of heal over leftovers.
as for the 4th moveslot, depends what you want, if you are running a trick room team then using trick room would give you the advantage of using aquatail which at base power 90 and with STAB thrown in, you have a very powerful attacker, as of course drain punch doesnt work on the many ghosts, if you are using yawn then you can force switches of course if you use a block passer you can utilize this to get that belly off safely, if you feel you dont need either then go for zen headbutt as a 2nd stab option which will widen any coverage defects, or for rain dance team, slap on rain dance and boost aqua tail further..
(i used metalkids calcualtor so not sure how accurate they are so dont rant at me if they are wrong...)
aqua tail (without rain boosts)
86.0% - 101.6% on registeel UU tank set
145.1% - 170.5% to supporting wall shuckle
259.3% - 306.5% to supporting tank rhyperior
100.7% - 118.4% on bold 252hp/252def spiritomb
drain punch calcs
76.9% - 90.7% on supporting wall registeel
98.5% - 116.2% on Calm mind clefable (bold 252hp 152def)
if for whatever reason you wish to use it in OU... blissey will of course probably try and cripple it.
104.9% - 123.5% to diversebliss (bold 148 HP / 252 Def) and a huge heal from the punch itself
this is by no means a complete set and is still rather gimmiky due to lack of options, in the physical movepool, i still think it can do well especailly in trick room and/or duel screens, aqua jet with rain of course will add even more to the aqua tail damage,
enjoy, if anyone can pick improvements then by all means, it has had very little testing (not at all in this form as i was experimenting with it and i never got to face the UU's that occur often)