Burn it with fire.
Agree with Exarach on this one. Find a pistol you like, buy a few mags, and you got a rocking CQB piece. Otherwise, go with a small AEG and some mids.
The 40mm's are fun, but it quickly becomes a question of finances. Since TAP is field BB only, you'll be shelling out for A LOT of Elite Force ammo. 60 rounds is better spent in an MP5 mid or 1911 GBB mag that you can direct each BB where it needs to go.
Alternatively, if you're still digging the multi-shot concept, check out a tri-shot spring or a 5-shot gas shotgun. They're both awesome close in fighting pieces. The tri-shots load from shells and are as much fun as you should be allowed to have. Traded mine a while back and miss it every now and again. You would be very well served with one of those.