This is the list and I don't know what they all are, but will add some I think.

Excluded Operations
account_witness_proxy_operation (can't assign a proxy to witness vote)
account_witness_vote_operation (can't vote for witnesses)
update_proposal_votes_operation (has to do with the SPS voting)
vote_operation (can't vote directly)
withdraw_vesting_operation (can't power down)
set_withdraw_vesting_route_operation (can't powerdown to another accont)
transfer_operation (can't transfer?)
limit_order_create_operation (internal market?)
limit_order_create2_operation (internal market?)
transfer_to_vesting_operation (can't power up)
transfer_to_savings_operation (can't move to savings)
escrow_transfer_operation (no idea)

They can delegate their stake to other accounts and those accounts could vote. This allows for example, mister delegation to support applications.