Connect to PgAdmin III via localhost I just want to login for first time, from pgAdmin III via localhost on openSuSE 13.1 64x.
My pg_hba.conf:


# TYPE  DATABASE        USER            ADDRESS                 METHOD

# "local" is for Unix domain socket connections only
local   all             all                                     trust
# IPv4 local connections:
host    all             all             127.0.0.1/32            ident
# IPv6 local connections:
host    all             all             ::1/128                 ident
# Allow replication connections from localhost, by a user with the
# replication privilege.
#local   replication     postgres                                peer
#host    replication     postgres        127.0.0.1/32            ident
#host    replication     postgres        ::1/128                 ident



postgres=# \l
                                  List of databases
   Name    |  Owner   | Encoding |   Collate   |    Ctype    |   Access privileges   
-----------+----------+----------+-------------+-------------+-----------------------
 mydb      | postgres | UTF8     | en_US.UTF-8 | en_US.UTF-8 | 
 postgres  | postgres | UTF8     | en_US.UTF-8 | en_US.UTF-8 | 
 template0 | postgres | UTF8     | en_US.UTF-8 | en_US.UTF-8 | =c/postgres          +
           |          |          |             |             | postgres=CTc/postgres
 template1 | postgres | UTF8     | en_US.UTF-8 | en_US.UTF-8 | =c/postgres          +
           |          |          |             |             | postgres=CTc/postgres
 test      | postgres | UTF8     | en_US.UTF-8 | en_US.UTF-8 |
The basic misunderstanding: "localhost" is not a local connection. Your "trust" line in pg_hba.conf is not applicable for your connection:

local   all   all   trust


That only applies for connections via Unix-domain socket. Best choice for you is to connect via this route. Per pgAdmin documentation:


  The host is the IP address of the machine to contact, or the fully
  qualified domain name. On Unix based systems, the address field may be
  left blank to use the default PostgreSQL Unix Domain Socket on the
  local machine, or be set to an alternate path containing a PostgreSQL
  socket. If a path is entered, it must begin with a “/”. The port
  number may also be specified.


Bold emphasis mine.

More about connecting without password in this related answer on SO:
Run batch file with psql command without password